The in vitro anticarcinogenic and antimitotic effects of propolis and mitomycin-C (MMC) on transitional carcinoma cell cultures were investigated. Tissue samples were obtained from 22 patients with bladder carcinomas, which were exposed to propolis (0.1 mL) and MMC (1.6 microL). The mean MI rates for control, propolis and MMC were 8.327 +/- 0.624, 6.990 +/- 0.519 and 5.423 +/- 0.479, respectively. The differences between the control and exposed cells were significant (p < 0.05). We conclude that exposure to propolis can decrease cell division and it may be used as an antimitotic and anticarcinogenic agent.