Nitroglycerin is a potent smooth muscle relaxant used for biliary tract dilation during ERCP, (Chelly, J) and has been recommended for treatment of biliary colic based on anecdotal experience and small case reports. Nitroglycerin effect is a result of the nitric oxide component of the medication which acts as a smooth muscle relaxant in vascular, bronchial, esophageal and biliary smooth muscles. [McGowan(1936), Chelly (1979),Toyoyama (2001)] The typical dose of nitroglycerin is 0.4 mg given sublingually in pill form or, more recently, in a metered spray form. In a case series reported by Hassel (1993), positive response times ranged from 20 to 60 seconds with duration of action of two to twelve hours. Sublingual nitroglycerin is most commonly used for treatment of chest pain related to insufficient cardiac perfusion. It has also been noted to relieve the pain of esophageal spasms. Nitroglycerin has an excellent safety profile if used in patients with adequate pretreatment blood pressures. [Newberry (2005), Nitroglycerine (2011), Nitro (2011), Wolters (2009)] This study proposes to compare sublingual 0.4 mg doses of nitroglycerin to placebo for the initial treatment of acute pain from suspected symptomatic cholelithiasis