BY 1978 SEVERAL STATES HAD ENACTED LEGISLATION MAKING THE POSSESSION OF SMALL AMOUNTS OF MARIJUANA A CIVIL OFFENSE PUNISHABLE BY FINE INSTEAD OF A CRIMINAL ACT. THE REVISED FEDERAL CRIMINAL CODE ALSO CONTAINS MODIFIED DECRIMINALIZATION PROVISIONS. MUCH ATTENTION HAS FOCUSED ON CHANGES IN ADOLESCENT DRUG USE THOUGHT TO BE CAUSED BY DECRIMINALIZATION. TWO SURVEYS CONDUCTED IN OREGON AND CALIFORNIA IN 1975 AND 1976 BEFORE AND AFTER DECRIMINALIZATION LAWS PROVIDE SOME DATA, BUT METHODOLOGICAL WEAKNESSES MAKE THE DATA INCONCLUSIVE. OTHER RESEARCH INDICATES THAT WHILE MARIJUANA USE IS HIGHEST AMONG YOUNG ADULTS, EXPERIENCES WITH THE DRUG BY HIGH SCHOOL STUDENTS HAVE INCREASED MARKEDLY. MARIJUANA USE APPEARS TO BE HIGHEST AMONG MALE YOUTHS AND PERSONS WITH HIGHER INCOMES AND EDUCATION WHO TEND TO BE FROM THE WEST OR URBAN AREAS. THE CALIFORNIA AND OREGON STUDIES REFLECTED SIMILAR TRENDS, FOUND ONLY MINOR INCREASES IN USE AFTER DECRIMINALIZATION, BUT DID NOT SURVEY AGE AT ONSET OF USE OR OTHER DRUGS. RESEARCH ON PATTERNS OF USE HAS BEEN LIMITED BUT PRELIMINARY ANALYSIS INDICATES THAT DECRIMINALIZATION WILL NOT INCREASE INTENSITIES OR DURATION OF USE AND THAT MOST MARIJUANA WILL CONTINUE TO BE TAKEN FOR SOCIAL AND RECREATIONAL REASONS. CRITICS HAVE BEEN CONCERNED THAT DECRIMINALIZATION WILL BE PERCEIVED AS APPROVAL OF MARIJUANA AND THAT MARIJUANA COULD CONTRIBUTE TO FUTURE DRUG OR ALCOHOL PROBLEMS. INADEQUATE CORRECTIONAL FACILITIES AND COURT COSTS HAVE BEEN CITED AS REASONS FOR DECRIMINALIZATION. A VALID CONCERN IS THE THREAT TO PUBLIC SAFETY FROM MARIJUANA USE BECAUSE IT IMPAIRS ABILITIES TO OPERATE A CAR OR AIRPLANE. OTHER AREAS FOR DEBATE INCLUDE THE EFFECTS OF MARIJUANA ON CRIMINAL BEHAVIOR, SEXUAL BEHAVIOR, AND PERFORMANCE AT SCHOOL OR WORK. THE LONG-TERM MEDICAL EFFECTS OF MARIJUANA REMAIN UNKNOWN, ALTHOUGH STUDIES HAVE FOCUSED ON THE DRUG'S EFFECT ON THE IMMUNITY SYSTEM, CHROMOSOMES, LUNG CELLS, AND BRAIN FUNCTIONING. FOOTNOTES ARE APPENDED. (MJM)