2,8-Dihydroxyadenine urolithiasis is an inherited disorder caused by adenine phosphoribosyltransferase deficiency. A fast, simple, sensitive and selective capillary zone electrophoretic method for diagnosis of 2,8-dihydroxyadenine urolithiasis in adenine phosphoribosyltransferase deficiency is described. The method is based on direct measurement of 2,8-dihydroxyadenine in untreated urine in phosphate buffer at pH 3.0 within 8 min. Under the given separation conditions 2,8-dihydroxyadenine is very well separated from other purine and pyrimidine substances and presents characteristic UV spectra which enable identification in case of doubt. The urine samples containing pathological 2,8-dihydroxyadenine could be successfully analysed in levels approaching those relevant for bioanalytical applications. The reliability of the method presented for screening of patients with adenine phosphoribosyltransferase deficiency is demonstrated on a urine sample of a patient with the defect who was already treated with allopurinol at the time of obtaining the sample. No interfering substances were found in 50 urine samples from healthy infants under the analytical condition described.