Patients with 2,8-dihydroxyadenine urolithiasis are either completely or partially deficient in adenine phosphoribosyltransferase activities. Patients with partial enzyme deficiencies, all of whom have been found among Japanese, are homozygotes having a unique mutant adenine phosphoribosyltransferase gene (APRT*J) in double dose (Japanese type deficiency). We have established B-cell lines from heterozygotes and homozygotes of complete and Japanese type adenine phosphoribosyltransferase deficiencies as well as normal individuals. Characterization of the cell lines indicated that all homozygous cells were deficient in adenine phosphoribosyltransferase function while all heterozygous and normal cells had functional adenine phosphoribosyltransferase.