A normal canine bladder model was used to compare the effects of red and green light whole bladder photodynamic therapy (PDT). Eighteen dogs were treated with Photofrin 1 mg/kg and whole bladder irradiation with red or green light at doses ranging from 20 to 60 J/cm2. Toxicity was assessed using cystometry, cystoscopy, and histopathology. Green light produced more significant vesical toxicity than red light, and this toxicity tended to vary with the light dose administered. Whole bladder PDT with green light at doses greater than 20 J/cm2 resulted in permanent reductions in bladder capacity. Conversely, a green light dose of 20 J/cm2 and red light doses ranging from 20 to 60 J/cm2 did not produce any significant permanent reductions in bladder capacity. Thus, while green light may be more toxic to the bladder than red light, there are distinct combinations of red or green light and Photofrin which can be used in the canine bladder to achieve mucosal degradation without causing permanent vesical dysfunction.