Hexachlorophene was fed to female adult Sherman strain rats at 500 ppm (25 mg/kg/day) for 14 and 10 weeks in two consecutive studies. After two weeks on the diet containing hexachlorohene, the rats developed leg weakness which progressed to paralysis in three to five weeks. After ten weeks on these diets in the second study, hexachlorophene was discontinued; the rats regained almost complete recovery of leg function within six weeks. The brains of the rats that had ingested hexachlorophene weighed significantly more than those of controls and returned to normal in six weeks. The lesions produced by hexachlorophene in the rat brains represented cerebral edema limited to the white matter, which resembles diffuse spongy deggeneration of the white matter of the brain described in infants.