The possible ill-effects of cannabis on the peripheral nervous system were examined in 27 male subjects with respect to their motor and sensory nerve conduction. They were classified by their previous cannabis use into casual and heavy users. The nerve conduction studies were done after a baseline period of five days and then repeated after a three-week period during which the subjects could acquire and smoke standardized cannabis cigarettes. The casual users smoked a mean of 54·3 and the heavy users a mean of 109·5, cigarettes during the smoking period. No deterioration of peripheral nerve function could be demonstrated.