By the acute oral route, formamide is practically non-toxic having an LD50 of 7.5 gm/kg in rats. When the compound was held in occluded contact with the skin of guinea pigs for 24 hours, it caused slight skin irritation. However, animals receiving 5 and more cc/kg died in 2 to 6 days. The animal receiving a dose of 1 cc/kg survived. Rabbits seen less susceptible to intoxication by the cutaneous routes; an LD50 of 17 gm/kg has been recorded for the species. In a standard test for skin sensitization in guinea pigs, 0/5 animals were sensitized. Rats exposed to atmospheric concentrations as high as 54 mg/L of the material evaporated from a 50% mixture of fornamide and methanol failed to demonstrate any signs for a period of six hours, and the weight gain in the subsequent two-veek observation period was essentially normal for animals of this size. Because of the differential in boiling points of methanol and formanide, it seems apparent that the vast majority of the material vaporized into the exposure chamber would have been methanol, and only a small portion of the exposure could be attributed to the formanide. When the undiluted compound was placed in the eye of a rabbit, it produced a mild, presumably reversible injury that was graded 4 on a scale of 1 to 10.