Oral ciprofloxacin might achieve higher concentration in urine than in serum; theoretically, this drug might act as an anticancer drug against bladder cancer cells. Among fluoroquinolones, ciprofloxacin is distinguished by strong inhibition of topoisomerase II. A good correlation between cytotoxic activity of ciprofloxacin toward eukaryotic cells and its ability to induce the cleavable complexes topoisomerase II-DNA has been demonstrated. These data provide a basis for supposing that ciprofloxacin may act as anticancer drug. The efforts of evaluating ciprofloxacin's influence on human bladder cell lines have been shown by many authors. The cells were exposed to ciprofloxacin at various concentrations that are attainable in the urine after oral drug administration. Antiproliferative potential of the ciprofloxacin against human bladder cells varies according to drug concentration and time of incubation. It seems that ciprofloxacin can act as an anticancer drug in eukaryotic cells. Low urine pH can enhance the antitumor effect of ciprofloxacin. Ciprofloxacin enhances the effect of action of doxorubicin and epirubicin, which are used to prevent bladder cancer recurrence after transurethral resection of superficial bladder cancer. We think that ciprofloxacin might be used for antibacterial prophylaxis and as an anticancer agent in patients with superficial bladder cancer. This idea must be checked in future placebo controlled trials.