THE NATIONAL YOUTH POLYDRUG STUDY SURVEYED 2,750 YOUTHS 12 TO 19 YEARS OF AGE ADMITTED TO TREATMENT FOR DRUG ABUSE DURING THE PERIOD OF SEPTEMBER 1976 TO MARCH 1977. BASED ON THE FINDINGS, YOUTHS IN DRUG TREATMENT PROGRAMS ACROSS THE COUNTRY ARE BEST CHARACTERIZED AS MULTIPLE RATHER THAN SINGLE SUBSTANCE ABUSERS. FOR THE PURPOSES OF THIS STUDY, 'MULTIPLE SUBSTANCE USE' IS DEFINED AS THE USE OF A VARIETY OF DRUGS EITHER CONCURRENTLY OR SEQUENTIALLY. USE OF NONOPIATE DRUGS AND TYPES OF OPIATES OTHER THAN HEROIN WAS FOUND TO BE MUCH MORE PREVALENT THAN USE OF HEROIN. FOR NEARLY ALL OF THE CLIENTS, THE MULTIPLE ABUSE PATTERNS INCLUDED THE USE OF MARIHUANA AND ALCOHOL. THOSE WITH THE SEVEREST MULTIPLE-DRUG INVOLVEMENT REPORTED THE USE OF ILLEGAL METHADONE. THE AVERAGE YOUNG DRUG ABUSE CLIENT REGURLARLY ABUSED APPROXIMATELY FIVE DRUGS PRIOR TO COMING INTO TREATMENT. SUBJECTS REPORTED THAT MOST OF THE DRUGS THEY USED WERE EASY TO OBTAIN, AND YOUNG FEMALES APPEARED TO HAVE AN EASIER TIME ACQUIRING DRUGS THAN DID YOUNG MALES. ALTHOUGH WHITE YOUTHS ARE SOMEWHAT UNDERREPRESENTED IN PUBLIC DRUG TREATMENT PROGRAMS IN RELATION TO THEIR NUMBERS IN THE GENERAL POPULATION, WHITES WERE FOUND TO ABUSE MORE DIFFERENT TYPES OF DRUGS MORE FREQUENTLY THAN BLACKS. IT IS CLEAR FROM THE DATA THAT MIDDLE-CLASS, SUBURBAN, AND URBAN WHITE YOUTHS REPRESENT A SIGNIFICANT MARKET FOR NONNARCOTIC DRUGS. THE DRUG CAREERS OF THE MAJORITY OF THOSE SURVEYED STARTED BEFORE 13 YEARS OF AGE. QUESTIONS NEEDING TO BE ADDRESSED AND RESEARCHED AS A CONSEQUENCE OF THESE FINDINGS ARE LISTED, AND IT IS NOTED THAT CURRENTLY THERE IS AN INSUFFICIENT UNDERSTANDING OF THE NATURE, EXTENT, AND PATTERNS OF MULTIPLE DRUG USE TO MOUNT LARGE EDUCATION/PREVENTION CAMPAIGNS OR TO ESTABLISH EXTENSIVE TREATMENT NETWORKS. SUPPORTING TABULAR DATA AND A BIBLIOGRAPHY ARE PROVIDED. (RCB)