PHENCYCLIDINE, ALSO KNOWN AS PCP, ANGEL DUST, AND HOG, IS AN ABUSED DRUG OF INCREASING SIGNIFICANCE BECAUSE OF ITS WIDESPREAD USE BY YOUTH. PCP RANKED SEVENTH IN CURRENT OR PAST USE AMONG THE 15 DRUG TYPES CONSIDERED IN THE STUDY. IT HAD BEEN USED MORE WIDELY AND FREQUENTLY THAN ALL DRUGS OTHER THAN ALCOHOL, MARIJUANA, HASHISH, AND AMPHETAMINES, BARBITURATES, AND HALLUCINOGENS. ITS USE WAS REPORTED IN INTERVIEWS BY 31.9 PERCENT OF THE MALES AND 31.7 PERCENT OF THE FEMALES IN THE TOTAL STUDY SAMPLE. WHITES CONSTITUTED 42.3 PERCENT OF THE PCP USERS AS COMPARED TO ONLY 8.5 PERCENT BLACKS, AND 9.0 PERCENT HISPANICS. MEAN AGE OF FIRST USE WAS 14.6. OF PCP USERS, 67 PERCENT REPORTED CONTINUED USE. PCP ABUSERS ARE MORE LIKELY THAN OTHER DRUG TYPE ABUSERS TO BE INVOLVED IN SIGNIFICANT POLYDRUG ABUSE; NO SUBJECT REPORTED USING ONLY PCP. ABOUT 50 PERCENT OF THE PCP ABUSERS WERE USING THE DRUG ON THE AVERAGE OF AT LEAST ONCE A WEEK FOR THE 3-MONTH PERIOD ASSAYED; 18.7 PERCENT REPORTED AT LEAST DAILY USE DURING THE 1 MONTH OF PEAK USE. PCP WAS REPORTED TO BE EASILY OBTAINABLE BY 55.5 PERCENT OF THE SUBJECTS, AND AVAILABLE BY AN ADDITIONAL 24.7 PERCENT. MALES MORE OFTEN MADE STREET BUYS FROM DEALERS, WHILE FEMALES WERE MORE LIKELY TO RECEIVE PCP AS A GIFT FROM A FRIEND. COMPARED TO NON-PCP USERS IN THE TOTAL STUDY POPULATION, PCP USERS ENGAGED IN MORE SELF-DESTRUCTIVE BEHAVIORS AS GUAGED BY OVERDOSES AND SUICIDE ATTEMPTS. THE PCP SUBSAMPLE ALSO APPEARS TO HAVE MORE PREVIOUS DRUG TREATMENT EXPERIENCE. PCP USERS ENTERED TREATMENT AT AN AVERAGE AGE OF 16.5 AND WERE SOMEWHAT LESS OFTEN REFERRED BY PEERS AND SOMEWHAT MORE OFTEN REFERRED BY JUDGES THAN WERE OTHER DRUG-TYPE USERS. CONTINUOUS PCP USE WAS FOUND TO BE ASSOCIATED WITH FAMILY-RELATED PROBLEMS AND PROBLEMS IN MAINTAINING SCHOOL ATTENDANCE AS A CONSEQUENCE OF FAMILIAL PROBLEMS AND/OR LEARNING DISABILITIES. EXTENSIVE COMPARATIVE AND OTHER STATISTICAL DATA ARE PRESENTED IN TABULAR AND GRAPHIC FORM. A DEMOGRAPHIC DESCRIPTION OF THE TREATMENT PROGRAM CLIENTS IS APPENDED. (JAP)