This study compares the treatment of patients with comorbid medical and psychiatric illness admitted to a high-acuity (Type IV) integrated medicine and psychiatry inpatient program with patients having psychiatric symptoms on general internal medicine wards (IMWs). More patients in the Type IV program had agitation, suicidal ideation, or psychosis as psychiatric admission behaviors when compared to IMW patients. Medical symptom improvement was comparable in the two settings, whereas, psychiatric symptoms improved more in the Type IV Program than on the IMWs despite more significant illness and comparable lengths of stay. Integrated care on the Type IV unit allowed shorter total lengths of stay for medical patients with serious psychiatric illness than would have occurred had the traditional sequential approach to care been used. The integrated Type IV medicine and psychiatry treatment program represents an efficient and effective process improvement in the way that medical patients with comorbid medical and psychiatric illness can be treated.