<PAGE>
PROSPECTUS SUPPLEMENT DATED MARCH 15, 2000 FILED PURSUANT TO RULE 424(b)(3)
(To Prospectus Dated October 1, 1999) SEC FILE NO. 333-84661
$100,000,000
ITC/\DeltaCom
4 1/2% Convertible Subordinated Notes Due 2006
This prospectus supplement relates to resales by the holders of ITC/\DeltaCom,
Inc.'s 4 1/2% Convertible Subordinated Notes due 2006 and the shares of
ITC/\DeltaCom's common stock, par value $.01 per share, issuable upon conversion
of the notes. This prospectus supplement should be read in conjunction with the
prospectus dated October 1, 1999, which is to be delivered with this prospectus
supplement.
The information appearing under the heading "Selling Holders" in the
prospectus is superseded in part by the information included in the table below.
<TABLE>
<CAPTION>
Principal Principal
Amount of Notes Amount of Common
Beneficially Notes Stock Owned Common
Owned Prior Offered Prior to the Stock Offered
Name to the Offering Hereby Offering(1) Hereby(2)
---- --------------- --------- ------------ -------------
<S> <C> <C> <C> <C>
Bear Stearns & Co......................... $ 1,375,000 $ 1,375,000 51,556 51,556
White River Securities LLC............... $ 1,375,000 $ 1,375,000 51,556 51,556
JMG Convertible Investments, L.P.......... $ 1,250,000 $ 1,250,000 46,869 46,869
Triton Capital Investments, Ltd........... $ 5,250,000 $ 5,250,000 196,850 196,850
LDG Limited............................... $ 150,000 $ 150,000 5,624 5,624
TQA Leverage Fund, L.P.................... $ 500,000 $ 500,000 18,747 18,747
TQA Vantage Fund, Ltd..................... $ 1,000,000 $ 1,000,000 37,495 37,495
TQA Vantage Plus Fund, Ltd................ $ 350,000 $ 350,000 13,123 13,123
Employee Benefit Convertible Securities
Fund..................................... $ 225,000 $ 225,000 8,436 8,436
Nations Capital Income Fund............... $ 3,150,000 $ 3,150,000 118,110 118,110
Forest Alternative Strategies Fund II LP
Series A 5 M............................. 105,000(4) $ 105,000 3,937(4) 3,937
Chase Manhattan N.A., Trustee for IBM
Retirement Plan dated 12/18/45........... $ 1,957,000(5) $ 1,957,000 73,378(5) 73,378
Value Line Convertible Fund, Inc.......... $ 500,000 $ 500,000 18,747 18,747
Alexandra Global Investment Fund I Ltd.... $ 3,000,000 $ 3,000,000 112,485 112,485
Conseco Senior Health Insurance Company -
Convertible.............................. $ 625,000 $ 625,000 23,434 23,434
Conseco Health Insurance
Company-Convertible...................... $ 625,000 $ 625,000 23,434 23,434
Conseco Funds Group - Convertible......... $ 1,000,000 $ 1,000,000 37,495 37,495
BNP Arbitrage SNC......................... $ 2,900,000 $ 2,900,000 108,736 108,736
Highbridge International LLC.............. $ 6,255,000(6) $ 6,255,000 234,533(6) 234,533
AFTRA Health Fund......................... $ 250,000 $ 250,000 9,373 9,373
Mainstay Convertible Fund................. $ 3,000,000(6) $ 3,000,000 112,485(6) 112,485
Coditec International Ltd. E (VBL)........ $ 50,000 $ 50,000 1,874 1,874
Faria Fund Ltd............................ $ 50,000 $ 50,000 1,874 1,874
Federated Utility Fund, Inc............... $ 7,700,000 $ 7,700,000 288,713 288,713
Federated Insurance Series, on behalf of
its Federated Utility Fund II............ $ 850,000 $ 850,000 31,871 31,871
SunAmerica Series Trust, on behalf of its
Federated Utility Portfolio.............. $ 470,000 $ 470,000 17,622 17,622
California Public Employees Retirement
System................................... $ 2,000,000 $ 2,000,000 74,990 74,990
First Mercury Insurance Company--Total
Return................................... $ 20,000 $ 20,000 749 749
Century National Insurance Company........ $ 300,000 $ 300,000 11,248 11,248
Nalco Chemical Company.................... $ 250,000 $ 250,000 9,373 9,373
State of Oregon Equity.................... $ 5,325,000 $ 5,325,000 199,662 199,662
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
Principal Principal
Amount of Notes Amount of Common
Beneficially Notes Stock Owned Common
Owned Prior Offered Prior to the Stock Offered
Name to the Offering Hereby Offering(1) Hereby(2)
---- --------------- --------- ------------ -------------
<S> <C> <C> <C> <C>
Delaware PERS............................. $ 1,400,000 $ 1,400,000 52,493 52,493
ICI American Holdings Trust............... $ 600,000 $ 600,000 22,497 22,497
Zeneca Holdings Trust..................... $ 600,000 $ 600,000 22,497 22,497
Pacific Life Insurance Company............ $ 1,000,000 $ 1,000,000 37,495 37,495
Pitney Bowes Retirement Fund.............. $ 2,000,000 $ 2,000,000 74,990 74,990
J.P. Morgan Securities Inc................ $ 1,500,000 $ 1,500,000 56,242 56,242
Convexity Partners LP..................... $ 750,000 $ 750,000 28,121 28,121
Sage Capital.............................. $ 1,300,000 $ 1,300,000 48,743 48,743
Boulder Capital, Inc...................... $ 358,000 $ 358,000 13,423 13,423
Boulder II Limited........................ $ 500,000 $ 500,000 18,747 18,747
Pebble Capital Inc........................ $ 142,000 $ 142,000 5,324 5,324
------------ ------------ --------- ---------
Subtotal................................. $ 62,007,000 $ 62,007,000 2,324,971 2,324,971
Unnamed holders of previously registered
notes(7)................................. $ 37,955,000 $ 37,955,000 1,423,134 1,423,134
Any other holders of notes or future
transferees from such holders(3)......... $ 38,000 $ 38,000 1,424 1,424
------------ ------------ --------- ---------
Total.................................... $100,000,000 $100,000,000 3,749,531 3,749,531
============ ============ ========= =========
</TABLE>
- -------------------------
(1) Comprises the shares of common stock owned by each selling holder prior to
the offering, including the shares of common stock into which the notes
held by the selling holder are convertible at the initial conversion rate
of $26.67 per share, excluding fractional shares. Fractional shares will
not be issued upon conversion of the notes; rather, cash will be paid in
lieu of fractional shares, if any. The conversion price and the number of
shares of common stock issuable upon conversion of the notes are subject to
adjustment under specified circumstances, which are described in more
detail in the accompanying prospectus under "Description of NotesConversion
of Notes." Accordingly, the number of shares of common stock issuable upon
conversion of the notes may increase or decrease from time to time.
(2) Assumes conversion into common stock of the full amount of notes held by
the selling holder at the initial conversion rate of $26.67 per share and
the offering of those shares by the selling holder pursuant to this
prospectus supplement and accompanying prospectus. The conversion price and
the number of shares of common stock issuable upon conversion of the notes
are subject to adjustment under specified circumstances which are described
in more detail in the accompanying prospectus under "Description of Notes -
Conversion of Notes." Accordingly, the number of shares of common stock
issuable upon conversion of the notes may increase or decrease from time to
time. Fractional shares will not be issued upon conversion of the notes;
rather, cash will be paid in lieu of fractional shares, if any. The selling
holders may offer and sell pursuant to the prospectus, their notes, the
shares of common stock into which the notes are convertible, or both.
(3) Information concerning other selling holders of notes will be set forth in
additional prospectus supplements from time to time, as required. No
holder may offer notes pursuant to the prospectus until such holder is
included as a selling holder in a supplement to the prospectus in
accordance with the registration rights agreement. Assumes that any other
holders of notes or any future transferee from any such holder does not
beneficially own any common stock other than common stock into which the
notes are convertible at the conversion price of $26.67 per share.
(4) Includes $100,000 principal amount of previously registered notes and the
common stock into which those notes are convertible.
(5) Includes $1,345,000 principal amount of previously registered notes and the
common stock into which those notes are convertible.
(6) Includes $1,000,000 principal amount of previously registered notes and the
common stock into which those notes are convertible.
(7) Based on information provided to ITC/\DeltaCom by the trustee as of
February 4, 2000. Excludes $3,445,000 principal amount of previously
registered notes identified in footnotes (4) through (6).
S-2
