This article discusses the utility and limitations of urethroscopy and cystoscopy in both male and female cats. The special equipment and techniques necessary to adequately visualize the urethra and bladder of female cats are described in some detail. The emerging ability to visualize the male urethra is introduced. Photographs taken through the cystoscope are used to illustrate both normal anatomy and lesions likely to be encountered with cats with lower urinary tract disease. Cystoscopy is an important diagnostic tool for an inclusionary and exclusionary diagnosis of interstitial cystitis (sterile idiopathic inflammation).