With the increase in the number of farm flocks, sheep have assumed an ever increasing role in veterinary practice. It has been said, and justly so, that a sheep is a difficult animal to treat. However, with the improvement in vaccines and pharmaceuticals, excellent results may be obtained if the original diagnosis is correct. With sheep, perhaps more than any other animal, a correct diagnosis is essential to successful treatment. A mistaken diagnosis and subsequent erroneous treatment may be disastrous.