The in vivo transformation of cannabinol (CBN) in the rat has been studied. Unchanged CBN and nine neutral mono‐oxygenated and dioxygenated CBN metabolites have been identified. In the mono‐oxygenated series the metabolites occurred in decreasing order of prominence as follows: 7‐hydroxy‐CBN, 4“‐hydroxy‐CBN, 1”‐hydroxy‐CBN, 2“‐hydroxy‐CBN, 3”‐hydroxy‐CBN, 5“‐hydroxy‐CBN and CBN‐7‐al. In the dihydroxylated metabolite series only 1”,7‐dihydroxy‐CBN and 4“,7‐dihydroxy‐CBN were found with the former as the more prominent metabolite.