The General Health Questionnaire (GHQ-12) and the Self Report Questionnaire (SRQ-20) were simultaneously validated against the criterion of the Revised Clinical Interview Schedule (CIS-R) in a primary care clinic in Santiago, Chile. A Relative Operating Characteristic (ROC) analysis was used to determine the optimal threshold point for case definition and to compare the performance of these two questionnaires. The validation coefficients for the GHQ-12 and the SRQ-20 were, respectively: sensitivity 76% and 74%; specificity 73% and 77%; overall misclassification rate: 26% and 25%. Misclassification by these questionnaires was significantly associated with education and sex, males being more likely than females to be misclassified as false negatives and poorly educated respondents as false positives. The symptom response profile of both questionnaires showed that the most prevalent items were psychological complaints of anxiety and depression. Both instruments seem to have a similar ability to identify minor psychiatric disorders in primary care in Chile.