Heterobilharzia americana was commonly found in raccoons and nutria from 3 localities in southern Louisiana and in all of 3 dogs examined from one area. Infection in one of the dogs was fatal. This is the first record of canine schistosomiasis in the Western Hemisphere. In all 4 host species, the worms were located in the veins of both small and large intestines and in the intrahepatic portal veins. Eggs were abundant in the wall of the intestines, and granulomata containing eggs were conspicuous in all parts of the liver. In the dog, eggs were also found in the lungs, kidneys and spleen.