Patients with disabling, persistent somatization pose significant challenges in clinical management. This study describes 92 patients treated on an inpatient psychosomatic medicine unit for persistent somatization. The most important factor in defining clinically significant subgroups of these patients was mood. Compared with depressed somatizing patients, nondepressed somatizing patients had chronic illnesses of early onset, had symptoms that were not correlated with current life stressors, and were generally unresponsive to treatment. There were few clinical predictors of treatment outcome apart from the duration of symptoms, the presence of mood disturbance, and a history of stable interpersonal relationships.