Nutritional secondary hyperparathyroidism occurred in 16 red fox kits (Vulpes vulpes) ranging in age from 8 to 10 weeks. The kits were thin and unthrifty. The canine teeth varied in appearance from dull-pink to dull-gray. Most kits were affected with a mild bilateral conjunctivitis and some degree of kyphosis. There were palpable bilateral enlargements of the distal epiphyses of the radius, ulna, and femur, and the costochondral junctions of the ribs. Two kits examined by necropsy had lesions of progressive fibrous osteodystrophy. In four of the kits, mean plasma calcium levels (8.3 mg/100 ml) were reduced in conjunction with a concomitant rise in the mean phosphorous level (7.4 mg/100 ml). The mean plasma urea nitrogen level (24.7 mg/100 ml) was elevated and the mean total protein content (4.6 gm/100 ml) was reduced. Mean plasma activity values for alkaline phosphatase (107.8 mU/ml), lactic dehydrogenase (355.5 mU/ml), and glutamic oxalaoacetic transaminase (896.8 mU/ml) were markedly elevated.