From a total sample of 1,448 psychiatric outpatients, 81 (5.6%) received a diagnosis of generalized anxiety disorder (GAD) according to DSM-III-R criteria. Fifty-three (65%) of them had another Axis I diagnosis, while this percentage increased to 78% (63/81) when lifetime psychiatric diagnoses were recorded. The most frequent comorbid diagnoses were panic disorder, dysthymia, major depression and social phobia. Forty-three (53%) of the GAD patients met the criteria for personality disorder. They manifested obsessive-compulsive, avoidant personality and personalities of cluster C in general significantly more frequently than the rest of the total sample. The presence of a personality disorder was related to a significantly higher score on almost all the Minnesota Multiphasic Personality Inventory clinical and research scales, to a worse level of functioning and to an earlier age of onset of GAD. The results of the present study (1) support previous findings of high rates of comorbidity of clinical syndromes in GAD, (2) indicate that GAD co-occurs frequently with cluster C personality disorders, mainly avoidant and obsessive-compulsive, and (3) that the presence of a concomitant personality disorder is related to severer psychopathology and to a worse level of functioning.