<PAGE>
FILED PURSUANT TO RULE 424(b)(3)
REGISTRATION NO. 333-86257
Supplement, Dated November 2, 1999, to Prospectus, Dated September 17, 1999,
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of UnitedGlobalCom, Inc.
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Additional Selling Securityholders. The following selling securityholders are
added to the list of selling securityholders in the prospectus:
<TABLE>
<CAPTION>
Number of Depositary Shares
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Name of Selling Securityholder Owned Offered
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<S> <C> <C>
Bank of America Securities LLC.................. 40,000 40,000
LDG Limited..................................... 8,000 8,000
NMS Services, Inc............................... 75,000 75,000
TQA Master Fund, Ltd............................ 115,200 115,200
TQA Master Plus Fund, Ltd....................... 89,000 89,000
Value Line Convertible Fund, Inc................ 10,000 10,000
</TABLE>
