Since 1973 we have used allopurinol in the prevention and aftercare of recurrent urolithiasis. We give indications for the administration of allopurinol for patients with chronically recurring calcium oxalate lithiasis. Special attention is given to the urinary stone analysis as well as to metabolic disorders as for example hyperuricaemia, hyperuricuria or idiopathic hypercalciuria. In 15 patients with calcium oxalate lithiasis the stone/patient/year ratio could be decreased to 38 %. In 19 patients with uric acid/ calcium oxalate calculi or alternating stone formations from uric acid and calcium oxalate we succeeded in decreasing this ratio from 1.72 to 0.47 or 27 %.