Personality disorders (PDs) are considered to be potential predictors of outcome and potential matching variables. In this report the authors review the available epidemiological studies regarding the overall prevalence of DSM-III(Pv) PDs in alcohol, cocaine, opiate and polydrug addicts in both patient and nonpatient samples. Special attention is paid to the prevalence of antisocial and borderline PDs. Fifty-two studies were identified covering the time period 1982–1994. The findings of these studies suggest that the best estimate of overall axis II prevalence ranges from 44% among alcoholics to 79% among opiate addicts. However, a wide range of prevalence rates was observed in all types of substance use disorders. These differences could only partly be accounted for by differences in primary substance of abuse, assessment procedure, and setting. Gender distribution, the alternate application of exclusion criteria, classification system and time-frame, seem to be other important factors in understanding the divergent findings.