In this study the antimicrotubular agents taxol, taxotere, and vinblastine were compared for their ability to inhibit the clonal growth of human bladder tumor cell lines using a soft-agar clonogenic assay. The stability of taxol and taxotere was evaluated by high-performance liquid chromatography over a range of pH in human urine. Both taxol and taxotere were shown to maximally inhibit the clonal growth of human bladder cell lines within 1 h of drug incubation. The most active agent in the panel of tumor lines was taxotere, with 6 of 12 lines being sensitive to the agent at 0.01 microM and all cell lines being sensitive at 0.1 microM. Taxol was active in 1 of 12 lines at 0.01 microM and in 11 of 12 at 0.1 microM. Only 2 of 12 cell lines were sensitive to vinblastine over the 0.01- to 0.1-microM dose range. Taxol and taxotere were found to be stable in human urine for 4 h over a pH range of 5-7. At least 85% of both drugs were present during this period of drug incubation. Our findings suggest that both taxol and taxotere may be clinically useful agents for systemic and intravesical use in bladder cancer.