This article reports two studies, where the accuracy of implicit personality theory (IPT) was investigated using on-line behavior counts as well as retrospective frequency estimates as standards of comparison Eight discussion groups, each comprising six members, were videotaped Their act frequencies with respect to 16 types of behavior were judged on-line using two coding schemes, each one being applied by two independent raters Five other judges estimated the act frequencies retrospectively Furthermore, judges revealed their IPT by estimating the conditional likelihood of these types of behavior It turned out that (a) retrospective judges perceive different base rates accurately, (b) the correlations among retrospectively estimated and among on-line recorded act frequencies show high correspondences, (c) IPT accurately mirrors the correlations among retrospectively estimated as well as among on-line recorded act frequencies, and (d) judges do not appropriately consider perceived base rates when estimating conditional probabilities It is concluded that IPT is considerably accurate in those respects that are important for the validity and structural fidelity of personality ratings