A total of 2090 treatment episodes from 1977 to 1990 at a therapeutic community for acute patients were assessed for group psychotherapy participation and its associations with some patient and program characteristics, based on polytomous logistic regression analysis. Nonparticipation (4% of all episodes) or passivity (14%) were associated mainly with the program properties (such as the quality of the ward policy, first treatment episode and short treatment time), a diagnosis of personality disorder or typical schizophrenia and inferior outcome (assessed by attainment of treatment goals). The associations of moderate activity (45%) were very active (37%) as a reference, mainly personal properties (such as male gender, young age, low social and professional background and a diagnosis of schizophrenia) and inferior outcome. The results suggest that group participation, therapeutic program, patient properties and attainment of treatment goals are interrelated. The therapeutic program and leaders' skills should be developed to facilitate individualized group participation.