A series of benzochlorins have been prepared and tested for tumoricidal activity using the FANFT-induced rat bladder tumor model. Results indicate that these chlorin derivatives, in combination with red light, can cause significant tumor regression at doses as low as 0.5 - 1.0 mg/kg body weight. This compares favorably with other sensitizers tested in the same model and suggests that further studies on the effectiveness of benzochlorins in photodynamic therapy be performed.