Bladder stones in men are thought to be almost exclusively due to outflow obstruction. We studied the incidence of operations for urinary outflow obstruction and bladder stone to establish the relationship between these two conditions in Kelantan. In only 48 (31%) of 154 men undergoing removal of bladder stones was a procedure for outflow obstruction performed. Thus the remaining 69% had no clinical obstruction to account for their stones. Bladder stones were more common in prostatectomy patients than expected (42/193: 22%). We suggest that other causes may be important in the aetiology of bladder stones in Kelantan.