It is mandated by P.L. 99-457 that parents be active participants on their children's interdisciplinary teams (Nash, 1990). An important part of these teams' work is to assess children's developmental needs and plan programs accordingly. Because information from parents can contribute to this assessment, it is reasonable to examine the quality of that information. Historically, the quality of parents' information has been inferred from the degree of congruence between their judgments and those of professionals. Some previous research suggests that parents' estimates of their children's abilities are higher than those of professionals (Sheehan, 1988). The purpose of this study was to conduct a literature review of congruence between parental estimates and professionals' assessments and identify factors that might affect the degree of congruence. The results suggest that (a) there are strong, positive correlations between parental and professional judgments, and (b) methodology relates to the degree of congruence between parental and professional judgments. Several cautions regarding interpretations of the accuracy and validity of parents' judgments based upon congruence estimates are examined.