Twenty patients with histologically documented superficial bladder cancer (Ta, T1, Tis) were treated with intravesical administration of TNF 400-1800 micrograms. Of 18 patients with a marker lesion, 2 obtained a complete response for 8+ and 18 months. Two had a partial response and were given other intravesical therapies after 5 and 7 months. No or minimal systemic absorption of TNF was observed and documented in 4 of 20 patients by pharmacokinetic studies, and no patients developed antibodies to intravesically administered TNF. TNF was well tolerated in doses up to 1800 micrograms. No systemic or local side effects were observed. Modest activity was attained with intravesical TNF, even in pretreated patients.