The psychoactive ingredients of cannabis are the terpenophenolic cannabinoids. The main psychoactive cannabinoid is tetrahydrocannabinol (THC). In Canada, seized cannabis products are submitted for THC analysis for court purposes. Data on cannabis potency is generally obtained from the analysis of law enforcement seizures. In the Netherlands, data have been derived from cannabis products purchased in coffee shops since 1999. A study on the THC content of fresh illicit cannabis products seized on entry into the United Kingdom was conducted by the Laboratory of the Government Chemist (LGC). Cannabidiol, the main non-psychotropic constituent of cannabis, does not bind to the cannabinoid receptors, probably exerting its effects through novel cannabinoid receptors mediating non-CB1/CB2 receptor effects. In conclusion, it is clear that high-potency cannabis products are freely available on the international drug markets, and that cannabis products have at least a two-fold increased THC content compared with pre-2000 products.