Microbial degradation of hexane vapor was tested in liquid cultures of Mycobacterium ID-Y and in a compost biofilter in the presence of Pluronic F68 (PF68). PF68, a nonionic block copolymer of ethylene oxide and propylene oxide, is water soluble, nontoxic, and relatively nonbiodegradable. PF68 was added at 0-20 wt % to enhance the aqueous solubility of hexane and thereby increase its degradation rate. The distribution coefficient of hexane (m = H-c/RT or CgC1) decreased by six times at 2.5 wt % PF68 with little additional decrease seen above 2.5 wt %. In liquid culture, PF68 increased specific growth rates of Mycobacterium ID-Yen hexane by about three times and increased the rate of hexane vapor degradation. Rates of hexane degradation were not increased however, in compost biofilters supplemented with 5.0 wt % PF68.