This study confirms the validity of a Spanish version of the General Health Questionnaire in its scaled 28-item version. The screening instrument was tested on a sample of 100 patients attending an internal medicine out-patient clinic, who were examined independently by psychiatrists standardized in the use of the Clinical Interview Schedule (CIS). The questionnaire correctly identified 85% of 'cases' with a cutting score of 6/7 (sensitivity 76.9%, specificity 90.2%), and 83% of cases with a cutting score of 5/6 (sensitivity 84.6%, specificity 82%), suggesting a discriminative power almost as good as the Spanish GHQ-60. It has the important advantage of being considerably shorter and, although the 4 subscales are by no means independent, its concurrent validity with CIS ratings suggests that they provide additional information concerning anxiety and depression.