Two new groups of photosensitizers, purpurins and metallopurpurins were tested for photodynamic activity when combined with visible light (>590nm), in the treatment of transplantable urothelial tumors (FANFT induced) in Fischer 344 rats. In preliminary studies, animals were injected with 10 mg/kg body weight (b.w.) of the free base purpurins (NT1, NT2, NT2H2, GG1, ET2, ET2H2 and JP1) and treated with 360J/cm2 of red light. Tumors were excised, fixed in formalin and stained for light microscopic examination. Purpurin based photodynamic therapy (PDT) was found to cause extensive hemorrhagic tumor necrosis. Control tumors shielded from the light showed no histological changes. These experiments were repeated using the same experimental design for the metallopurpurins (ZnET2, SnET2, ZnNT2H2, SnNT2H2, AgNT2H2 and ZnNT1). These compounds were also found to cause extensive hemorrhagic necrosis. These studies were followed by a dose response analysis in which groups of animals were treated with decreasing doses of drug while the light dose was kept constant. Response was determined by tumor dry weight, 12 days after completion of PDT. For the free base purpurins, drug doses as low as 1.0 mg/kg b.w. caused significant tumor regression while seleted metallopurpurins caused tumor regression at doses as low as 0.5 mg/kg b.w. In a series of related experiments the effect of purpurins on tumor blood flow was investigated since it has previously been shown that tumor blood flow is disrupted during porphyrin and phthalocyanine phototherapy. By using the radioactive microsphere technique, it was shown that both the free base purpurins and metallopurpurins caused a rapid decrease in tumor blood flow.