The biosynthesis of biotin-vitamers from C18 fatty acids in the resting cell reaction system of yeasts was investigated. The formation of pimelic acid (a biotin precursor) and biotin-vitamers (a mixture of 7-keto-8-aminopelargonic acid and dethiobiotin) from linolenic, linoleic, and oleic acids was observed in certain yeasts belonging to the genera Cryptococcus, Candida, Rhodotorula, and Trichosporon. Metabolites from linolenic acid were analyzed by gas-liquid chromatography and mass spectrometry. Linoleic, oleic, stearic, heptadecanoic, palmitic, pentadecanoic, and pimelic acids were identified as metabolites of linolenic acid. The existence of a route to pimelic acid from linolenic acid in a strain of Rhodotorula rubra AKU 4836 was also indicated.