There are few cytogenetic studies of early (non-invasive) bladder cancer, particularly in sifu carcinoma, due to technical difficulties in examining such lesions. The best approach is to extrapolate from chromosomal changes in more advanced cancers. Although no specific chromosomal changes have been established in either early or fully developed bladdercancers, certain recurrent anomalies have been encountered. Anomalies such as +1, +7, -9,5q-or i(5p), 1 lp-and -Y appear to constitute part of the multistep carcinogenetic process by which clinically and pathologically recognizable bladder cancers develop. Since loss of part or all of chromosome 9 (-9) is a common and early cytogenetic event in bladder cancer, the detection of -9 in bladder washings or urine by fluorescence in sifu hybridization (FISH) may be a promising test for early or recurrent bladder cancer. Although less frequent than -9, trisomy 7 (+7) is common enough to serve a similar purpose. In contrast, loss of the Y chromosome may indicate an advanced stage of bladder cancer. Thus, FISH studies utilizing probes for chromosomes 7.9, and Y should yield cogent information to identify early bladder cancer. Cytogenetic (including FISH) studies combined with certain molecular approaches (e.g., p53 mutations detected immunochemically) may not only serve to differentiate early cancer from benign tumors orconditions, but may also help establish cancer stage. This would supply data of considerable usefulness to the clinician and pathologist.