Twenty-three patients with superficial transitional cell carcinoma of the urinary bladder were randomized for intravesical chemotherapy with either cis-platinum or cis-platinum plus hyaluronidase, an enzyme promoting diffusion factor. Treatment was administered at 3-week intervals and checked for efficacy by repeated cystoscopies after every three instillations. Hematologic and biochemical tests were repeated prior to each treatment and, these, in additional to the cystoscopic findings, served for final evaluation of results and toxicity. The complete response rate was found to be superior with cis-platinum than with cis-platinum plus hyaluronidase. The complete plus partial response rates were equal in both groups. We conclude that the addition of hyaluronidase to cis-platinum revealed no superiority to cis-platinum alone, and both modes of treatment showed similar clinical efficacy as other drugs previously used for intravesical chemotherapy.