Entamoeba invadens was studied in 3 species of snakes at temperatures of 13-14 and 25 C. Infected snakes of all species failed to show any gross pathology at 13 C, although amoebae were isolated from the snakes by culture. At the higher temperature all species showed pathological changes, most severe in Natrix, dekayi and red belly, and progressively less severe in the garter, milk, ribbon, ringneck and green snakes. For the last 5 species, the pathology in the liver and intestine was so characteristic as to provide an adequate basis for identification of the snake. Snakes infected at the lower temperature and later transferred to 25 showed the same pathological changes as those kept at 25 throughout. The possible effects of behavior patterns of snakes on pathogenicity of the amoebae are pointed out.