<TABLE> <S> <C>

<ARTICLE> 6
<LEGEND>
This schedule contains Summary Financial Information extracted from the Form
N-SAR and the financial statements and is qualified in its entirety by
references to such documents.
</LEGEND>
<SERIES>
   <NUMBER> 022
   <NAME> NUVEEN NATIONAL INSURED MUNICIPAL BOND FUND - CLASS B
<MULTIPLIER> 1000

<S>                             <C>
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          APR-30-2001
<PERIOD-START>                             MAY-01-2000
<PERIOD-END>                               OCT-31-2000
<INVESTMENTS-AT-COST>                           731496
<INVESTMENTS-AT-VALUE>                          772025
<RECEIVABLES>                                    14839
<ASSETS-OTHER>                                      20
<OTHER-ITEMS-ASSETS>                                 0
<TOTAL-ASSETS>                                  786884
<PAYABLE-FOR-SECURITIES>                          4415
<SENIOR-LONG-TERM-DEBT>                              0
<OTHER-ITEMS-LIABILITIES>                         4719
<TOTAL-LIABILITIES>                               9134
<SENIOR-EQUITY>                                      0
<PAID-IN-CAPITAL-COMMON>                        751648
<SHARES-COMMON-STOCK>                             1824
<SHARES-COMMON-PRIOR>                             1646
<ACCUMULATED-NII-CURRENT>                          574
<OVERDISTRIBUTION-NII>                               0
<ACCUMULATED-NET-GAINS>                        (15001)
<OVERDISTRIBUTION-GAINS>                             0
<ACCUM-APPREC-OR-DEPREC>                         40529
<NET-ASSETS>                                    777750
<DIVIDEND-INCOME>                                    0
<INTEREST-INCOME>                                23454
<OTHER-INCOME>                                       0
<EXPENSES-NET>                                    2689
<NET-INVESTMENT-INCOME>                          20765
<REALIZED-GAINS-CURRENT>                        (1264)
<APPREC-INCREASE-CURRENT>                        16704
<NET-CHANGE-FROM-OPS>                            36205
<EQUALIZATION>                                       0
<DISTRIBUTIONS-OF-INCOME>                          392
<DISTRIBUTIONS-OF-GAINS>                             0
<DISTRIBUTIONS-OTHER>                                0
<NUMBER-OF-SHARES-SOLD>                            335
<NUMBER-OF-SHARES-REDEEMED>                        174
<SHARES-REINVESTED>                                 17
<NET-CHANGE-IN-ASSETS>                            3125
<ACCUMULATED-NII-PRIOR>                            360
<ACCUMULATED-GAINS-PRIOR>                      (13737)
<OVERDISTRIB-NII-PRIOR>                              0
<OVERDIST-NET-GAINS-PRIOR>                           0
<GROSS-ADVISORY-FEES>                             1863
<INTEREST-EXPENSE>                                   0
<GROSS-EXPENSE>                                   2715
<AVERAGE-NET-ASSETS>                             17928
<PER-SHARE-NAV-BEGIN>                            10.35
<PER-SHARE-NII>                                    .23
<PER-SHARE-GAIN-APPREC>                            .21
<PER-SHARE-DIVIDEND>                             (.23)
<PER-SHARE-DISTRIBUTIONS>                            0
<RETURNS-OF-CAPITAL>                                 0
<PER-SHARE-NAV-END>                              10.56
<EXPENSE-RATIO>                                   1.58


</TABLE>