RECORDS OF 1747 PATIENTS ADMITTED TO THE METHADONE MAINTENANCE PROGRAM WERE EXAMINED; 1-YEAR TREATMENT COHORTS WERE ESTABLISHED TO STUDY CHANGES IN PROGRAM ADMINISTRATION OVER THE 5-YEAR PERIOD. MEAN EDUCATION OF PATIENTS REMAINED AT 10.5 YEARS OVER THE LIFE OF THE PROGRAM; 79 PERCENT OF PATIENTS WERE BLACK, 70 PERCENT MALE, 42 PERCENT NEVER MARRIED, AND MEAN AGE AT ADMISSION WAS 30 YEARS. CONSIDERABLE VARIATION WAS FOUND BETWEEN THE PROGRAM DEFINITION OF TERMINATION AND THE RECOMMENDED DEFINITION UNDER FOOD AND DRUG ADMINISTRATION (FDA) GUIDELINES. THE PROGRAM CONSIDERED A PATIENT TERMINATED IF METHADONE WAS MISSED 20 OR MORE TIMES IN A 2-MONTH PERIOD, BUT SUCH PATIENTS WERE READMITTED IF THEY RETURNED EVEN AFTER PROLONGED ABSENCE. FDA REGULATIONS DECLARE A PATIENT TERMINATED IF 14 DAYS ARE MISSED. THIS STUDY ADOPTED THE PROGRAM DEFINITION, BUT DID NOT CONSIDER A READMISSION AFTER A PERIOD OF TIME A VALID CONTINUATION. UNDER PROGRAM DEFINITION, 26 PERCENT DROPPED OUT BEFORE 12 MONTHS, 20 PERCENT REMAINED 12-24 MONTHS, AND 28 PERCENT REMAINED FOR 36 MONTHS, THE RECOMMENDED TREATMENT PERIOD. WITHOUT CONSIDERING READMISSIONS, 37 PERCENT TERMINATED BEFORE 12 MONTHS, ANOTHER 30 PERCENT TERMINATED 12-24 MONTHS, AND 23 PERCENT STAYED FOR 36 MONTHS. THE HIGHER RETENTION RATES WERE FOUND IN THE FIRST PART OF THE PROGRAM. IT IS SUGGESTED THAT THE LAX REENTRY PROVISIONS LED PATIENTS TO BELIEVE THE RULES WERE NOT STRICTLY ENFORCED. AS A RESULT, A HABIT OF 'DROPPING IN' FOR METHADONE REMOVED THEM FROM THE SOCIAL AND COUNSELING ASPECTS OF THE PROGRAM. THIS IS INDICATED BY THE LOWER EMPLOYMENT RATES, HIGHER CRIME RATES OF PATIENTS UNDER TREATMENT, AND LOWER ADJUSTMENT OF EACH SUCCEEDING TREATMENT COHORT. THE ONE DETERMINANT WHICH REMAINED HIGH WAS MORPHINES IN URINE; THIS INDICATED THAT A LARGE NUMBER OF THE PATIENTS WERE NOT USING HEROIN IN SUCH QUANTITY AS TO BE PRESENT IN THE URINE. THE RESULTS OF THIS PROGRAM CANNOT BE COMPARED WITH OTHER PROGRAMS BECAUSE EVALUATION CRITERIA VARY SO WIDELY. IT IS SUGGESTED THAT UNIFORM DATA COLLECTION METHODS AND DEFINITIONS BE ESTABLISHED.