There is growing evidence that substance abuse is a major problem in patients with schizophrenia. With respect to alcohol, alledegly the most frequently abused drug among schizophrenics, clinical and epidemiological studies would suggest that the risk of alcoholism is approximately four times greater (Cuffel, 1992; Mueser et al., 1990; Soyka et al., 1993; Soyka, 1994). A variety of hypotheses have been proposed to explain this phenomenon, including the so-called "self-medication hypothesis". Some authors feel that substance abuse in schizophrenics might be due to extrapyramidal and other side-effects caused by neuroleptic treatment or inadequate remission of psychotic symptoms. There remains, at present, an obvious lack of both psychosocial and psychopharmacological studies of treatment in "dual diagnosis" schizophrenics (Mueser et al., 1992). Changes in dopaminergic neurotransmission and dopamine-receptor dysfunction have been linked both to the development of psychotic symptoms and to alcoholism/substance abuse, and thus give rise to the question as to whether some dual diagnosis patients might benefit from neuroleptic treatment in both domains. A number of dopamine receptor subtypes in different regions of the brain seems to be involved in the development of schizophrenia and substance abuse. Modifications of D2-receptor subtype function have been implicated in psychotic symptoms, and changes in the D1- and D2-receptor function in substance abuse such as cocaine abuse and alcoholism (Spealman et al., 1990; 1991; 1992), especially in the mesolimbic dopaminergic reward system. Accordingly, the "ideal" neuroleptic drug for dual diagnosis schizophrenics should be effective in both receptor subtypes.(ABSTRACT TRUNCATED AT 250 WORDS)