<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
FINANCIAL STATEMENTS OF LARSCOM INCORPORATED FOR THE SIX MONTHS ENDED JUNE 30,
2000 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> JUN-30-2000
<CASH> 13,555
<SECURITIES> 15,545
<RECEIVABLES> 9,219
<ALLOWANCES> (514)
<INVENTORY> 6,422
<CURRENT-ASSETS> 51,948
<PP&E> 19,821
<DEPRECIATION> (15,633)
<TOTAL-ASSETS> 68,124
<CURRENT-LIABILITIES> 13,293
<BONDS> 0
0
0
<COMMON> 186
<OTHER-SE> 54,052
<TOTAL-LIABILITY-AND-EQUITY> 68,124
<SALES> 27,838
<TOTAL-REVENUES> 27,838
<CGS> 12,961
<TOTAL-COSTS> 16,991
<OTHER-EXPENSES> 0
<LOSS-PROVISION> 0
<INTEREST-EXPENSE> (836)
<INCOME-PRETAX> (1,278)
<INCOME-TAX> (378)
<INCOME-CONTINUING> (900)
<DISCONTINUED> 0
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> (900)
<EPS-BASIC> (0.05)<F1>
<EPS-DILUTED> (0.05)
<FN>
<F1>REPRESENTS BASIC EARNINGS PER SHARE
</FN>
</TABLE>