The stability of nitroglycerin tablets that had been stored in hospitals across the United States was studied. Through a voluntary FDA drug stability program, all hospital pharmacies in the United States were asked in October 1981 to complete a response card indicating information about nitroglycerin tablets they had in stock. Based on the responses, FDA selected 167 samples (representing three manufacturers and all available tablet strengths) from pharmacies that represented an adequate cross section of the country. The samples were analyzed for content uniformity, strength, identification, and disintegration; samples that left a residue on the screen of the tablet disintegration basket were tested for dissolution by three methods and compared with samples that did not leave a residue. All samples met USP requirements for content uniformity, strength, and disintegration. Six samples that showed unusual disintegration characteristics dissolved slowly by one or more methods; however, other samples also showed slow dissolution. Nitroglycerin tablets appear to be stable when stored under actual marketplace conditions. The USP disintegration test will not distinguish between rapidly and slowly dissolving tablets.