The proliferation and migration of cells is a fundamental process for the metastasis of malignant tumour cells. In several in vitro studies, pertussis toxin (PTX) inhibited cell proliferation and cell motility in the human transitional cell carcinoma cell line J82. The present study investigated the effect of the intravesical application of PTX on the development of superficial bladder cancer in rats. We used the model of N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN, 0.05% via drinking water x10 weeks) to induce superficial bladder carcinomas in 40 female rats. After 16 weeks the rats were treated in two groups with 0.4 ml PTX (1 microg/ml) or 0.4 ml phosphate buffered saline (PBS) by intravesical application (once a week for 10 weeks). In the 25th week urine cytology was determined and all rats were killed at week 26 followed by histological evaluation. In the control group, the urine cytology was positive for G2/G3 cells in ten of 17 rats. In the PTX group G2/G3 cells were determined in five of 20 rats ( P two tailed <0.05). Histopathologically 12 rats (71%) of the control group and 11 rats (55%) of the PTX group developed T1-T2 transitional-cell carcinomas. No local or systemic side effects were disclosed. PTX treatment reduces the development of G3 transitional cell carcinomas in rats and may represent a new approach for local therapy in superficial bladder cancer.