The present study examines a self-report version of the Global Assessment of Functioning Scale according to Axis V (GAF self-report). The sample (n = 73) was a psychiatric outpatient population from a catchment area clinic. Patients with psychotic and organic mental disorders were not included. The diagnostic distribution on Axis I was similar to the findings from previous studies. Axis II disorders were identified among 47%, of whom a majority also had a concomitant Axis I disorder. The mean GAF expert score was 66.5 (range: 48-86). High complexity and severity of disorders and a high number of fulfilled Axis II criteria were significantly associated with low GAF scores. Independent expert ratings on GAF were correlated with the GAF self-report overall at r = 0.62, varying from 0.45 to 0.91 between different diagnostic groups. In general, the patients scored themselves lower (mean: -4.4 units) than expert ratings. Patients with depressive symptoms from an adjustment disorder or mood disorder were most prone to underestimation. Women also tended to score themselves lower than experts did. Conclusively, the GAF self-report turned out to be a valid and reliable unidimensional instrument measuring psychological, social and occupational functioning. The GAF is easy to handle, and with a self-report version as a complement, Axis V could be more frequently used in future clinical practice and research.