THE 37 SUBJECTS IN THE STUDY ATTENDED THE CLINIC DURING 1976, AND THE AGE RANGE OF THE SAMPLE WAS FROM 15 TO 59 YEARS. OF THE SUBJECTS, 16 WERE DEPENDENT ON HEROIN OR METHADONE, 6 WERE DEPENDENT PRIMARILY ON BARBITURATES OR OTHER SEDATIVES, AND 15 WERE MULTIPLE DRUG ABUSERS FOR WHOM THERE WAS NO PRIMARY DRUG OF DEPENDENCE. ALL SUBJECTS WERE ASKED TO COMPLETE THE EYSENCK PERSONALITY QUESTIONNAIRE, AND A SELF-REPORTED FORENSIC HISTORY OF EACH SUBJECT WAS ALSO OBTAINED THROUGH INTERVIEW. MORE THAN HALF OF THE SUBJECTS HAD AT LEAST ONE CONVICTION. OF CONVICTED SUBJECTS, 15 HAD BEEN CONVICTED OF AT LEAST ONE DRUG-RELATED OFFENSE AND 14 HAD BEEN CONVICTED OF DRUG-RELATED AND NONVIOLENT CRIMES. ONLY FOUR SUBJECTS HAD BEEN CONVICTED OF ANY VIOLENT CRIME. THE MOST FREQUENTLY RECORDED OFFENSE WAS SHOPLIFTING; THE SECOND MOST COMMON OFFENSE WAS FORGERY OF PRESCRIPTIONS. PERSONALITY SCORES OF THE SAMPLE AS A WHOLE WERE HIGH. THE PREDICTION THAT CONVICTED FEMALE ADDICTS SHOULD SCORE HIGHER ON EXTRAVERSION THAN NONCONVICTED SUBJECTS WAS SUPPORTED BY SEVERAL RESULTS. SUBJECTS WITH CONVICTIONS ON THE OTHER OFFENSES VARIABLE WERE MORE EXTRAVERTED THAN NONCONVICTED SUBJECTS. THERE WAS A SLIGHT BUT NONSIGNIFICANT DIFFERENCE IN EXTRAVERSION BETWEEN CONVICTED AND NONCONVICTED SUBJECTS IN THE DRUG OFFENSES CATEGORY. ON THE TOTAL OFFENSES VARIABLE, CONVICTED SUBJECTS WERE SIGNIFICANTLY HIGHER ON EXTRAVERSION THAN NONCONVICTED SUBJECTS. ORAL DRUG USERS SCORED HIGHER ON NEUROTICISM AND ON COMPOSITE CRIMINALITY SCALE THAN INTRAVENOUS DRUG USERS. EXTRAVERSION WAS POSITIVELY CORRELATED WITH THE TOTAL NUMBER OF CONVICTIONS, THE NUMBER OF CONVICTIONS FOR DRUG OFFENSES, AND CONVICTIONS FOR OTHER OFFENSES. THE FINDINGS OF THE STUDY MERELY POINT TO ONE ASPECT OF CRIMINALITY AND DRUG ADDICTION THAT HAS BEEN NEGLECTED. IN SUCH COMPLEX AREAS OF DRUG DEPENDENCE AND CRIMINAL BEHAVIOR, NO SINGLE FACTOR CAN BE EXPECTED TO PROVIDE A SATISFACTORY EXPLANATION. SUPPORTING DATA AND REFERENCES ARE INCLUDED. (DEP)