The National Institute of Forensic Toxicology routinely receives blood and urine samples from all Norwegian drivers arrested for driving under the influence of alcohol or drugs. In 1983, the institute received samples from 1,446 drivers, out of which 445 underwent toxicological analysis. The drugs most frequently detected were tetrahydrocannabinol (199), diazepam (166), and amphetamine (102). Approximately 200 of the 445 subjects were under the strong influence of drugs. Because of the high percentage of submitted cases not analyzed for drugs, the findings are a minimum estimate. In 1978, 894 blood and urine samples were received by the institute, out of which 426 were analyzed for drugs. Compared to 1978, 1983 manifested a several-fold increase in detections of tetrahydrocannabinol and amphetamine. The number of diazepam detections did not similarly increase, but the diazepam detections would probably have increased three-fold if the analyses for this drug in 1983 had been as frequent as in 1978. 3 tables, 2 figures, and 7 references.