The present study evaluated the efficacy of an Assertive Community Treatment (ACT) program for the seriously mentally ill. Outcomes of the program were assessed at baseline and 12-month follow-up and were compared with that of a control group, which received standard community care. Thirty-six subjects with serious mental disorders participated in the study. Dependent measures included number of hospital admissions and hospital bed days per year, life skills, quality of life, and psychiatric symptoms. Results of 2 x 2 (treatment/control group x baseline / 12-month follow-up) repeated measures ANOVAs indicated that, after 1 year, both treatments lead to a significant reduction in hospital admissions and bed days, and to improvement in life skills. ACT subjects evidenced a greater decrease in psychiatric symptoms compared to control group subjects. In general, markedly more ACT subjects showed reliable clinical change in life skills, quality of life, and psychiatric symptoms than control subjects. Although the ACT did produce greater clinical change than standard case management, it did not produce statistically greater improvement across most domains of functioning in the short term.