Mutations in the tumor suppressor gene p53, analyzed in bladder washings, have positive predictive value for the progression of superficial bladder cancer to invasive disease. Bladder washings reflect the general status of the urothelium, and because sampling of bladder washings can be performed as an outpatient procedure, patients can be monitored more carefully. To determine the actual value of bladder washing specimens in assessing the p53 status of histologic specimens, we used the technique of polymerase chain reaction-single-strand conformation polymorphism to analyze bladder washings and the synchronous tumors of 15 patients for the presence of p53 mutations. A significant correlation (2-tailed Fisher’s exact test) between the p53 status of bladder washings and histologic specimens was observed if the 2 were compared among the specimens of a single patient. Overall, in 2 patients the mutation present in the tumors was not detected in the bladder washings, and in 1 patient the mutation in the bladder washing was not detected in the histologic specimens. These conflicting results obtained with bladder washings and histologic specimens could be explained mainly by the architecture of the tumors. The observed specificity of 86% and sensitivity of 75% emphasizes that although the correlation between the 2 methods is good, in a number of cases they are complementary to each another. The analysis of p53 mutations in at least 2 bladder washings gives insight into the p53 status of the synchronous tumors.