Patients and their families are randomly assigned to either the Family Intervention for Dual Diagnosis (FIDD) program or family psychoeducation. The FIDD program lasts for up to 3 years and includes both single and multiple-family group formats. The family psychoeducation program consists of 6 weekly sessions. Routine assessments are conducted on all patients, and relatives are evaluated on a wide range of outcomes, including substance abuse, hospitalizations, psychiatric symptoms, legal problems, aggression, housing and homelessness, family burden, social support, and quality of life. To determine the effectiveness of the FIDD program, knowledge of mental illness and problem-solving skills are assessed in the families following treatment.