<ARTICLE> 5 <CIK> 0000931755 <NAME> AEI INCOME & GROWTH FUND XXI LIMITED PARTNERSHIP <PERIOD-TYPE> 6-MOS <FISCAL-YEAR-END> DEC-31-1999 <PERIOD-END> JUN-30-1999 <CASH> 254,266 <SECURITIES> 0 <RECEIVABLES> 0 <ALLOWANCES> 0 <INVENTORY> 0 <CURRENT-ASSETS> 254,266 <PP&E> 18,793,585 <DEPRECIATION> (1,074,225) <TOTAL-ASSETS> 17,973,626 <CURRENT-LIABILITIES> 426,963 <BONDS> 0 <PREFERRED-MANDATORY> 0 <PREFERRED> 0 <COMMON> 0 <OTHER-SE> 17,546,663 <TOTAL-LIABILITY-AND-EQUITY> 17,973,626 <SALES> 0 <TOTAL-REVENUES> 961,415 <CGS> 0 <TOTAL-COSTS> 419,673 <OTHER-EXPENSES> 0 <LOSS-PROVISION> 0 <INTEREST-EXPENSE> 0 <INCOME-PRETAX> 541,742 <INCOME-TAX> 0 <INCOME-CONTINUING> 541,742 <DISCONTINUED> 0 <EXTRAORDINARY> 0 <CHANGES> 0 <NET-INCOME> 541,742 <EPS-BASIC> 22.51 <EPS-DILUTED> 22.51