A total of 71 fecal samples, collected from 56 animal species (47 mammals, four reptiles, and five avians), were examined for the occurrence of Bacillus thuringiensis. Most of the animals were residents of the Fukuoka Municipal Zoo, Fukuoka, Japan. The organism was detected in 32 (45%) samples. Among 2, 955 colonies of the Bacillus cereus/B. thuringiensis group examined, 531 (18%) were assigned to B. thuringiensis on the basis of the formation of parasporal inclusions. Fecal samples from animals feeding on vegetable matter contained B. thuringiensis at high frequencies. Examples included feces from the chimpanzee, gorilla, Japanese black bear, polar bear, green iguana, and ostrich. In contrast, only a few isolates were recovered from feces of carnivorous animals, in particular, feline mammalians including the lion, tiger, leopard, and jaguar. The results suggest that a daily food intake of plant origin yields the feces containing B. thuringiensis at high levels.