The Symptom Check-List-90-R (SCL-90-R) is a widely used psychological status symptom inventory. The properties of the German SCL-90-R version were studied in two clinical samples: psychosomatic outpatients and primary care patients. The data were compared with a German community sample. The internal consistency, measured by Cronbach's alpha coefficients, was found to be high, for the global scale and all original subscales. Mokken scale analysis indicated hierarchical structure for most of the subscales. Concurrent validity, evaluated by studying the relationship between the SCL-90-R subscales and the Inventory of Interpersonal Problems (IIP-C) and the General Health Questionnaire (GHQ-12) was also high. On the basis of receiver operating characteristic (ROC) analyses, it was found that the SCL-90-R was able to differentiate between subjects known to have a given psychological disorder and those who do not. Results of exploratory and confirmatory factor analysis failed to support the original nine factor model and two subsequent factor models. The strong interdependence of the original subscales and the strong first unrotated factor of the exploratory factor analyses raised concern regarding the multi-dimensionality of the SCL-90-R subscales. We concluded that the SCL-90-R is a useful tool for measuring psychological status, measuring change in outcome studies, or screening for mental disorders.