Abstract: In an important embodiment, the present invention concerns a method for detecting compulsive disorder susceptibility of a human. The method comprises initially obtaining a DNA sample of said human and then determining the presence or absence of a particular human D.sub.2 receptor gene allele in said sample. Detection of said allele in the sample is indicative of susceptibility to compulsive disorder. A most preferred embodiment is to detect a susceptibility to alcoholism and cocaine dependence, particularly because said allele has been found to be present in a majority of clinically diagnosed alcoholics and cocaine users. The human D.sub.2 receptor gene A1 and B1 alleles are most preferably detected in said sample.

Abstract: In an important embodiment, the present invention concerns a method for diagnosing compulsive disease predisposition of an individual. The method comprises initially obtaining a DNA sample of said individual and then determining the presence or absence of a particular human D.sub.2 receptor gene allele in said sample. Detection of said allele in the sample is indicative of predilection to compulsive disease. A most preferred embodiment is to detect predisposition to alcoholism, particularly because said allele has been found to be present in a majority of clinically diagnosed alcoholics. The human D.sub.2 receptor gene A1 allele is most preferably detected in said sample.