Developmental and gender differenced in relations between drug use and problem behaviour were examined among 2,619 adolescents in grade 7 to 12 who comprised the school population of a small midwestern city. Incidence rates of drug use were consistent with patterns reported elsewhere. Grade-related differences were found for 10 of the 18 substances investigated including the medical use of drugs; there were fewer gender differences. Problem behaviour was associated with the most extensive use of different substances among grade 9 students and the least among older adolescents. Of all the drug studied, alcohol use showed the highest association with problem behaviour. Greater drug experimentation was found among girls than boys in relation to their involvement in problem behaviour.