It has been argued that increased levels of treatment for drug abuse are effective in reducing the levels of drug problems. During the 1980s in Ontario levels of treatment increased considerably. More treatment facilities were opened, and the number of drug abuse cases increased by a factor of about seven. It was expected that drug-related problems (mortality, morbidity, and convictions) would decrease, as happened for alcohol problems when alcohol treatment levels increased. However, the results were inconsistent. Hospital separations for drug problems decreased in the late 1970s and then increased in the 1980s. However, deaths from drug psychoses and drug dependency showed an opposite trend. Convictions for cocaine offences increased while those for narcotics, LSD, and hallucinogenic drugs showed a substantial decline from the early 1980s to the present. Significant negative correlations (suggestive of a beneficial impact) were found between treatment rates and three drug-problem measures (deaths rates from drug psychoses and drug dependence, other drug-related deaths, and convictions under the Food and Drug Act); however, a significant positive correlation was found between treatment rates and Narcotic Control Act convictions. Thus, although some of the predicted negative relationships between treatment rates and drug problems were observed, the correlations did not provide a consistent picture of the effects of increased drug treatment. More research is needed to identify better indicators of drug problems and monitor the factors that influence them.