Validity coefficients of the 12-item General Health Questionnaire (GHQ-12) were established against the Clinical Interview Schedule (CIS) in a sample of primary care patients. Comparison between the conventional scoring method, Likert scoring, and the revised scoring procedure proposed by Goodchild and Duncan-Jones (C-GHQ) showed very similar screening properties: sensitivity ranged between 71% and 75%, and specificity ranged between 73% and 76%. The test-retest reliability of the GHQ-12, as expressed by Pearson's r and intraclass correlation coefficient, was satisfactory irrespective of the scoring method used, even though mean scores on the second test tended to be significantly lower than the corresponding mean scores on the first test. The C-GHQ by itself did not result in an improvement of the screening capacity of the GHQ; however, the best results were obtained by combining the conventional scoring and C-GHQ case criteria.