The hexitol mannitol produced a dose dependent inhibition of oxygen consumption when incubated with arachidonic acid and soybean lipoxygenase. This was associated with an inhibition of conversion of 1-[14C] arachidonate to 1-[14C] 15 hydroperoxy 5,8,11,13 eicosatetraenoic acid and an inhibition of conjugated diene formation followed spectrophotometrically. The IC50 was 38 mMol. A maximum of 50% inhibition O2 consumption was produced by glucose when added to incubation of soybean lipoxygenase with arachidonate. These findings are interpreted in the light of the known effect of mannitol in preventing acute renal failure and its potential role as a scavenger of free hydroxyl radicals. © 1982 Academic Press, Inc.