The most commonly encountered nutritional bone disease is nutritional secondary hyperparathyroidism. This is primarily of importance in the dog but is occasionally seen in kittens, particularly of the Siamese breed, and is often associated with the feeding of owner compiled, meat-rich diets. Classic rickets is now a rare clinical entity. Hypertrophic osteodystrophy is regularly seen in the larger breeds of dog and the aetiology remains obscure. Hypervitaminosis A associated with liver-rich diets is often encountered in the cat. Hypovitaminosis A has been described but its true clinical significance is unknown.