Cannabinoids from three samples of cannabis obtained from the Pitt-Rivers Museum, Oxford, and dating from the turn of the century were examined by gas chromatography and mass spectometry for the presence of cannabinoids. Although the samples were from different geographical locations, the profiles of constituent cannabinoids were similar. In common with other aged material, most of the cannabinoid content was present as cannabinol (CBN), the main chemical degradation product of the major psychoactive constituent, delta-9-tetrahydrocannabinol (delta-9-THC). However, a substantial concentration of CBN acid-A was also present; this compound is unstable to heat and readily undergoes decarboxylation to CBN. Methyl and propyl homologues of CBN, together with delta-9-THC and its naturally occurring acid-A were also found at low concentrations in all samples. Intermediates in the formation of CBN from delta-9-THC, previously identified in aged solutions of the drug, were absent or present in only trace concentrations. However, oxidation products involving hydroxylation at the benzylic positions, C-11 and C-1', not seen in solution, were identified in substantial abundance. The results suggest that decomposition of cannabis samples may proceed more slowly than originally thought.