THE INMATES' MEAN AGE WAS 18.8 YEARS; MEAN EDUCATION WAS 9.7 YEARS. EXPERIENCE SCALES USED WERE PEARSON'S NOVELTY-EXPERIENCING SCALE, PEARSON'S DESIRE-FOR-NOVELTY SCALE, AND VANDO'S REDUCER-AUGMENTER SCALE. DRUGS FOR WHICH USE HISTORIES WERE GATHERED INCLUDED CANNABIS, PSYCHODELICS, AMPHETAMINES, BARBITURATES, AND NARCOTICS. MULTIPLE SET FACTOR ANALYSIS WAS USED TO ANALYZE THE DATA. RESULTS INDICATED THAT THE REPORTED USE OF ALL DIFFERENT KINDS OF PSYCHOACTIVE DRUGS INTERCORRELATED SO HIGHLY AS TO CONSTITUTE ESSENTIALLY A SINGLE DRUG USE DIMENSION. IN ADDITION, THE PREDICTOR SET'S EXPERIENCE SEEKING MEASURES (EXTERNAL SENSATION SEEKING, INTERNAL COGNITIVE EXPERIENCE SEEKING, INTERNAL SENSATION SEEKING, AND EXTERNAL COGNITIVE EXPERIENCE SEEKING), WERE CONCEPTUALLY DISTINCT. MOREOVER, DRUG USE WAS MOST COMMON AMONG THOSE WHO WERE ATTRACTED TO UNUSUAL STATES OF CONSCIOUSNESS AND TO PHYSICALLY THRILLING ACTIVITIES, WHO LACKED CURIOSITY, WHO WERE STIMULUS--INTENSITY REDUCERS, AND WHO WERE SOMEWHAT BORED AND DISSATISFIED WITH THEIR LIVES. OF THESE CHARACTERISTICS, ATTRACTION TO UNUSUAL STATES OF CONSCIOUSNESS WAS THE MOST PREDICTIVE. FURTHER RESEARCH ON THE APPLICABILITY OF THESE FINDINGS TO OTHER POPULATIONS, AS WELL AS ON THE GENERAL TRANSFER OF THE FINDING THAT USE OF PSYCHOACTIVE DRUGS IS LARGELY UNIDIMENSIONAL, IS RECOMMENDED. TABLES, REFERENCES NOTES, AND A REFERENCE LIST ARE INCLUDED. (CFW)