This thesis attempted to determine if there were personality characteristic differences, as measured by the MMPI, between drug abusers who left treatment prematurely and drug abusers who remained in treatment for an extended period of time. In addition, it was attempted to determine if there were personality characteristic differences between drug abusers who entered treatment voluntarily and drug abusers who were required by law to obtain treatment.The MMPI protocols of 59 male drug abusers were divided into four groups and subjected to a two by two multivariate and Univariate Analysis of Variance. Results show that no significant differences were found between drug abusers admitted voluntarily and drug abusers admitted involuntarily. Significant differences were found between drug abusers who left treatment prematurely and drug abusers who remained in treatment for an extended period of time. Drug abusers remaining in treatment scored higher on scales Two, Seven, and Eight of the WI, while drug abusers who left treatment scored higher on the Lie scale. Suggestions for future research were made.