The conversion of beta-myrcene to the furanoid flavour compound perillene by Pleurotus ostreatus was investigated using trideutero beta-myrcene, trideutero alpha-(Z)-acaridiol and non-labeled 1,2- and 3,10-epoxy-beta-myrcene, alpha,alpha-acarilactol, and perillene as substrates. Myrcene diols were formed from the cleavage of myrcene epoxides, but only alpha-(Z)-acaridiol, a 1,4-butanediol derivative most likely generated through a base-catalysed epoxide opening, was a suitable precursor of perillene. Once formed, this key intermediate was rapidly oxidised and the resulting cyclic lactol was dehydrated to yield perillene. Bioconversion of the supplemented perillene to alpha,alpha-acariolide indicated that perillene was another intermediate of the pathway and prone to further oxidative degradation. The data suggest that the fungus converted the cytotoxic beta-myrcene in its environment into a metabolically useable carbon source along this route.