Photodynamic therapy with dihematoporphyrin ether was used to treat superficial bladder tumors in 7 patients with a followup of at least 1 year. Each patient received treatment to the whole bladder and those with papillary lesions received additional focal treatment. At 3 months 4 of the 5 patients with papillary tumors (stages Ta and T1) and 1 of the 2 with diffuse carcinoma in situ (Tis) were free of disease. However, at 1 year only 3 patients remained free of disease. Of 5 patients with an increase in irritative bladder symptoms 4 had a contracted bladder, hydroureteronephrosis and vesicoureteral reflux. Deep bladder biopsies showed replacement of smooth muscle by fibrous tissue. Six patients had mild to moderate skin phototoxicity. We conclude that although photodynamic therapy is an attractive and exciting method to treat cancer, its use with dihematoporphyrin ether in cases of bladder carcinoma can be associated with significant complications. The correct treatment parameters for safe, effective therapy are not known to date.