This study examined the ability of seven patient characteristics to predict success (remaining, benefiting) in a day treatment program for psychiatric outpatients. The sample consisted of 165 patients, most with affective and personality disorders, who participated in an intensive psychodynamically and group-oriented program within a controlled clinical trial. Two patient personality characteristics (psychological mindedness, quality of object relations) emerged as the strongest predictors. Other variables that contributed to the predictions, either singly or in an interaction with quality of object relations, were age, marriage, presence of a personality disorder, and previous psychiatric hospitalization. The patient's initial level of symptomatic disturbance was not a significant predictor. The advantage of using predictors that are relevant to the theoretical and technical orientation of a program is emphasized.