Two brothers with oligosymptomatic mucopolysaccharidosis VII were observed from age 11 8/12 to 16 years, and 15 1/2 to 19 years, respectively. Asymptomatic thoracic kyphosis and mild scoliosis were the prominent clinical features. Herniae, hepatosplenomegaly, corneal clouding and shortness of stature were absent. Both had Alder type granulations in polymorphonuclear leukocytes and to a lesser degree in monocytes. Ultrastructural analysis of blood leukocytes revealed polymorphous inclusions of probably more than one class of organic substances. Radiological signs were mild, confined to the spine and consisted of irregularities of upper and lower vertebral plates, of vertebral flattening and some osteophytic changes. Both patients excreted excessive amounts of acid mucopolysaccharides in urine and also globoside. Cultured skin fibroblasts of both patients contained metachromatic granules, had only approx. 10% of normal beta-glucuronidase activity and degraded sulfated mucopolysaccharides at a slower than normal rate. Sera of the patients had none or minimal beta-glucuronidase activity, the mother's serum had subnormal and the father's serum low-normal activity. The older brother is the oldest known case of mucopolysaccharidosis VII. As this hereditary disorder may take a remarkably mild clinical course, beta-glucuronidase-deficient juveniles may exist undetected in the general population.