NUMEROUS RESEARCH PROJECTS HAVE CLAIMED THAT ADDICTS ARE UNABLE TO DELAY GRATIFICATION OF NEEDS, ARE SUSCEPTIBLE TO PEER PRESSURES, AND CANNOT COPE WITH FRUSTRATION AND AGGRESSION. THESE HYPOTHESES WERE TESTED IN A CONTROLLED LABORATORY SITUATION USING 45 MALES AND 30 FEMALES DIVIDED INTO GROUPS OF 15 NONADDICT NONDELINQUENTS AND 15 ADDICTS. MALE SUBJECTS INCLUDED AN ADDITIONAL 15 NONADDICT DELINQUENTS. EACH GROUP HAD EQUAL NUMBERS OF ANGLOS, BLACKS, AND CHICANOS. ADDICTS WERE SOLICITED UPON ADMISSION TO A DETOXIFICATION CENTER; NONADDICT DELINQUENTS CAME FROM A PRERELEASE PROGRAM AT A LOCAL PRISON; AND NONADDICT, NONDELINQUENT SUBJECTS ANSWERED NEWSPAPER ADVERTISEMENTS. AT THE INITIAL SESSION, PARTICIPANTS COMPLETED A DEMOGRAPHIC QUESTIONNAIRE AND SEVERAL PERSONALITY TESTS. SUBJECTS THEN PERFORMED THREE TASKS USING A CUSTOM-BUILT HUMAN TEST CONSOLE CONTROLLED BY A MICROCOMPUTER. THE FIRST TASK PROVIDED PARTICIPANTS WITH CHOICES BETWEEN A SMALL, IMMEDIATELY DELIVERED AWARD AND A LARGER, DELAYED AWARD. THE SECOND TASK MEASURED THE AFFECT OF PEER AND NONPEER SOCIAL PRESSURES UPON PERFORMANCE. AT THE CONCLUSION OF THE TESTS, URINE SAMPLES WERE COLLECTED AND ANY SUBJECT WHOSE ANALYSIS INDICATED THE PRESENCE OF A MORPHINE-BASED DRUG WAS ELIMINATED. THE PERSONALITY TESTS INDICATED THAT THE SUBJECTS WERE TYPICAL OF THE POPULATIONS FROM WHICH THEY WERE SELECTED. BOTH MALE AND FEMALE ADDICTS CHOSE THE IMMEDIATE REWARD IN TASK ONE MORE OFTEN THAN THE OTHER GROUPS. ALL SUBJECTS WERE INFLUENCED BY SOCIAL PRESSURE, WITH ADDICTS MORE SUSCEPTIBLE TO NONPEER PRESSURE. PERFORMANCES CONTRADICTED THE THEORY THAT ADDICTS LACK ENDURANCE AND PERSISTENCE. ETHNIC ORIGIN WAS NOT A SIGNIFICANT FACTOR IN ANY TESTS. FURTHER STUDIES ON BEHAVIOR DIFFERENCES COULD ASSIST IN DEVELOPING MORE EFFECTIVE TREATMENT PROGRAMS. TABLES AND GRAPHS ILLUSTRATE DATA ON THE PERSONALITY TESTS AND TASK PERFORMANCES. FOOTNOTES AND REFERENCES ARE PROVIDED. (MJM)