Superficial transitional cell carcinoma is defined as a transitional cell urothelial tumor that is confined to the mucosa, stages Ta or CIS, or with invasion of the lamina propria, T1. The initial treatment is transurethral resection with an attempt to remove all tumor. This should provide an accurate histologic grade and stage, and from this information a prognosis can be determined. The important predictive factors that correlate with a new occurrence or true recurrence and the development of a subsequent tumor with muscle invasion are a high tumor grade, lamina propria invasion, a positive cytology following resection, multifocal tumors, dysplasia or carcinoma in situ from mucosal biopsies of normal appearing urothelium, and a prior history of bladder cancer. Based on these factors, the recurrence rate varies from 30 to 80% and progression with a muscle invasive tumor up to 30%. Intravesical chemotherapy or "immunotherapy" following tumor resection has been shown to diminish the likelihood of a recurrence. Thiotepa has been used for the longest period of time. It is relatively inexpensive, safe if myelosuppression is closely monitored, and effective. Mitomycin C was more effective than Thiotepa in randomized trials, but is significantly more expensive. This has retarded its use as a first-line agent. It has been shown to eradicate persistent tumor in 30 to 40% of patients who have failed Thiotepa. Mitomycin C is also highly effective when used for prophylaxis. Intravesical bacillus Calmette-Guerin (BCG) has recently been demonstrated to be an effective intravesical therapeutic agent. It is effective both for treatment and prophylaxis. BCG is relatively safe and inexpensive.(ABSTRACT TRUNCATED AT 250 WORDS)