The article begins with a review of the high prevalence of concurrent mental illness and chemical abuse (MICA) disorders among clinical populations, highlighting the need for development of appropriate services to treat these persons. This is followed by a description of a partial hospitalization program developed at the University of Rochester Medical Center-Strong Memorial Hospital, established to treat MICA patients. The program description includes information pertaining to the mission of the program, treatment setting, staffing, schedule, and diagnostic and sociodemographic data on 50 consecutive patients admitted to the program. It includes a review of the major goals of the program and the manner in which each of these goals is addressed. This is followed by a discussion of several arguments for the inclusion of patients with personality disorders in MICA treatment when there is concurrent substance abuse. It concludes with a case vignette of a patient treated in the MICA program.