To investigate the incidence of the H-ras gene activation in bladder tumor and the feasibility of using urinary washout samples for screening, a series of 33 human bladder tumors and their preoperatively collected urinary washout samples were screened using a mutant specific PCR-RFLP (polymerase chain-restriction fragment length polymorphism) to detect a point mutation of the H-ras gene. Five tumors were found to harbor H-ras mutations where two tumors had a glycine to valine (G-->T) change in codon 12 and three tumors had a glutamine to lysine (C-->A) change in codon 61, respectively. Moreover, we could also detect the same point mutations of the H-ras gene in corresponding urine washout samples. The incidence of H-ras mutation in Korean bladder cancer was estimated at approximately 15.2%. In conclusion, a mutant specific PCR-RFLP method for the detection of H-ras gene mutation is useful for screening or postoperative follow-up of bladder tumor due to its simplicity and high specificity even in urinary samples.