Patients with both alcoholism and mental illness, or the one masquerading as the other, are very common and often puzzling and discouraging to clinicians. This article reviews several aspects of these problems: epidemiologic studies show that substantial proportions of mentally ill people suffer from alcoholism, and these disorders interlock in complex ways, each exacerbating the other. Many physicians feel uncomfortable working with alcoholic people, mostly because of poor training, and this impinges on difficulties of giving excellent care to these taxing patients. Complexities and resistances to interviewing obstruct evaluation. Interviewing and history taking techniques and the reason for them are discussed. The decision whether a patient needs medical or psychiatric hospitalization, alcoholism rehabilitation, or outpatient psychiatric or alcoholism treatment is reviewed along with the management and sequencing of treatment for primary and secondary alcoholism with concomitant psychosis, mania, depression, panic disorder, and adult attention deficit disorder. Clinical intervention and referral for the patient on a medical or surgical floor who may have alcoholism is discussed. Two special clinical problems, the differential diagnosis of postdetoxification depression and the risks of using alcohol cross-tolerant drugs, are also reviewed.