Oak poisoning has been recognized for over 300 hundred years. It occurs sporadically in many parts of the world. In the United States, most cases of oak poisoning are seen in the Southwest, Northeast, and Midwest. The leaves, buds, twigs, and acorns of many oak species are toxic, and all of them produce similar clinical signs and lesions when consumed in large enough quantities. Cattle are most often involved clinically, but sheep, horses, goats, rabbits, and quinea pigs are also susceptible.