We use administrative records from several Federal and State programs to evaluate the accuracy of reported program participation in the 2008 panel of the Survey of Income and Program Participation (SIPP).  We study rates of misreporting (rates of both false negatives and false positives), errors in reported benefit amounts, and misreporting about participation dynamics.  We also investigate determinants of misreporting and the within-person and within-household dynamics of misreporting. Finally, we compare misreporting in 2008 SIPP to misreporting in field tests of a newly re-designed SIPP survey instrument.