Adenine phosphoribosyltransferase(APRT) deficiency is an autosomal recessive disorder and the homozygotes develop 2,8-dihydroxyadenine(DHA) urolithiasis and, in severe cases, renal failure. The prevalence is higher among the Japanese than other ethnic groups. So far 120 cases have been reported among the Japanese. The disease is classified into 2 types; type I and II are associated with complete and partial deficiencies, respectively. While all non-Japanese cases were of type I, about 78% of the Japanese patients were of type II. Each of the type II patients has at least one APRT*J allele with a ATG(Met) to ACG(Thr) base substitution at codon 136. All APRT*J alleles were derived from a single ancestor. All type I patients and some type II patients possess APRT*QO alleles with various point mutations or large gene abnormality. Type II patients tend to develop first symptoms later than the type I patients. The diagnoses of homozygotes and heterozygotes can be done by the cell culture methods. Both enzyme assay and molecular diagnostic methods are useful but not as reliable as the cell culture methods Excessive water intake, restriction of foods with high adenine contents and administration of allopurinol are useful treatments.