Renal calculi that reside in caliceal diverticula are difficult to treat. Numerous treatment modalities have been used, including extracorporeal shock wave lithotripsy, laparoscopy, and percutaneous treatment. All therapies directed at fragmenting the stones are limited by the ability of these fragments to pass through the narrow diverticular neck. More recently, the retrograde approach using small-caliber flexible ureteroscopes has been applied successfully in the treatment of diverticular calculi. A description of our retrograde technique is presented. The ultimate success of this technique is dependent upon familiarity with the basic principles of ureteroscopy and successful clearance of stone fragments from the diverticulum.