Differences in demographic and social characteristics and treatment history of 407 patients age 55 or older were examined in relation to diagnosis. Seven diagnostic groups in three mental health service programs were studied, all of which were characterized by surprisingly high rates of previous treatment (75 percent overall). Patients in the dysthymia, adjustment disorder, and V code groups appeared to be the most similar and to have the greatest psychosocial resources and fewest indicators of chronicity. Schizophrenic and bipolar patients had the least resources and most indicators of chronicity. Substance abuse patients tended to live alone, while those with major depression seemed to have more resources and later onset of their illness than schizophrenic and bipolar patients. About half of those with milder diagnoses had received prior outpatient treatment, suggesting that perhaps past treatment success leads older adults to revisit mental health services.