Plants of the genus Cannabis are known to produce stronger and more immediate effects when smoked, the usual way of administration in Western countries, than when orally taken in similar amounts. In particular, the psychoactive effects are stronger than could be expected from the initial tetrahydrocannabinol (THC) content (Galanter et al. 1973). Therefore, it is important to investigate the products obtained following smoking instead of concentrating on the toxicology of the natural constituents.