A dihydroxyketone, now named phthiodiolone A, isolated from crude phthiocerol, is shown to be a mixture of homologues having the structure CH3·[CH2]n·CH(OH)·[CH2]4·CH(CH3)·CO·CH2·CH3 where n is 22 and 20, respectively. The same structure has been previously suggested as the probable structure for “phthiodiolone.”