The presence of human papillomavirus (HPV) was detected in transitional cell carcinoma of the urinary bladder. PCR amplification of DNA from 71 tumors, using consensus primers for a fragment of the L1 gene, detected 6 strongly positive tumors (through ethidium bromide staining of a gel) and 22 moderately positive tumors (through Southern blotting of the amplified DNA) for a total of 28 (39%) of the tumors. The presence of HPV was correlated with grade but not stage of the tumors. Typing of HPV was performed on 31 tumors: all positive tumors contained HPV 16 DNA except for one Ta tumor which contained HPV 11 DNA. Our data also showed a large variability in the sensitivity of HPV DNA detection, depending on sample fixation, DNA preparation, and amplification conditions, which may explain in large part the discrepancies reported in the literature on the association of HPV to bladder cancer. Because of the low HPV DNA copy number observed in bladder tumors, our results suggest that HPV should ideally be tested on fresh or frozen tumor material, that SDS detergent should be avoided for the preparation of DNA, and that the amplification conditions are critical for optimal detection.