In this paper, false-negative and false-positive cases of depressive illness are examined, differentiating levels of disagreement between a primary care physician's diagnosis and a standardized research diagnosis. Two stratified random samples of primary care patients in Seattle, USA (N = 373) and Groningen, The Netherlands (N = 340) were examined with the Composite International Diagnostic Interview-Primary Health Care Version (CIDI-PHC). Physician's severity ratings and diagnosis of psychological disorder were obtained. Three levels of disagreement between physician and CIDI diagnosis were distinguished: 1) complete disagreement about the presence of psychiatric symptoms (true false-negative and true false-positive patients); 2) disagreement over severity of recognized psychological illness (underestimated or overestimated); and 3) disagreement over the specific psychiatric diagnosis among those given a diagnosis (misdiagnosed or given another CIDI diagnosis). All three levels of disagreement were common. Only 27% of the false-negative cases were due to complete disagreement (true false-negatives), and 55% of the false-positives were due to complete disagreement (true false-positives). The true false-negative patients were younger, more often employed, rated their own health more favorably, visited their doctor for a somatic complaint and made fewer visits than the underestimated, misdiagnosed, and concordant positive patients. Complete disagreement in depressive diagnoses between the primary care physician and research interview is not as frequent as indicated by an undifferentiated false-negative/ false-positive analysis. Differentiating levels of disagreement does more justice to diagnostic practice in primary care and provides guidance on how to improve the diagnostic accuracy of primary care physicians.