We examined the level of agreement between diagnoses derived from data gathered by lay interviewers using the Diagnostic Interview Schedule (DIS) in a general population survey (the Epidemiologic Catchment Area project) and both DIS and clinical diagnoses made by psychiatrists. Overall percent agreement between the lay DIS and the psychiatrists clinical impression ranged from 79% to 96%. The chance-corrected concordance was .60 or better for eight of the 11 diagnoses. Specificities were all 90% or better. Sensitivities were lower, but lay results showed a bias for only two diagnoses: major depression was significantly underdiagnosed and obsessive illness was overdiagnosed. We compared the present results with those of previous studies from clinical settings. We explored possible reasons for disagreement and discussed the implications of the findings for psychiatric epidemiologic research.