Virtual cystoscopy was performed in 13 patients with hematuria and abnormal findings at conventional cystoscopy. Perspective volume-rendering algorithms were applied to helical computed tomographic data to generate interactive, intraluminal views of the bladder mucosa after insufflation of room air. At conventional cystoscopy, 29 masses appeared to arise from the bladder mucosa and two were hypertrophied median lobes of the prostate. At virtual cystoscopy, 30 masses arose from the bladder (one prostate mass was misinterpreted as an intrinsic bladder mass). Results at virtual cystoscopy were comparable to those at conventional cystoscopy but were obtained without the associated risks.