beta-glucuronidase deficiency is an extremely rare disorder which is known to have a considerable phenotypic variation. A survey of the clinical findings in 19 previously reported patients with mucopolysaccharidosis VII is presented together with the results of clinical and biochemical studies in two further patients. Because a similar clinical picture is present in a heterozygotic sister it is doubted whether all signs and symptoms can be attributed to the beta-glucuronidase deficiency. The probability of a concomitant disorder is discussed. Diagnosis was made both by demonstration of the deficiency in plasma and leucocytes, and by means of hair root analysis. The phenotypic variation and the fact that increased levels of glycosaminoglycans were not found in the urine of the two patients lead to the suggestion that in certain cases a correct diagnosis may be missed if the beta-glucuronidase activity in plasma and leucocytes is not determined and only routine urine investigation is performed as a screening for a mucopolysaccharidosis. Hair root analysis may be a useful method to measure the beta-glucuronidase activity.