The objective of this study was to evaluate the stability of radiopharmaceuticals compounded using activities and expiration times in excess of manufacturers' recommendations. Proof of the compounded sterile preparation quality when compounding outside of manufacturers' recommendations has become a key component of maintaining compliance with the guidelines set forth in United States Pharmacopeia General Chapter <797> Pharmaceutical Compounding-Sterile Preparations, originally released in 2008. Seven commercial nuclear pharmacies compounded various radiopharmaceuticals for patient use as part of daily pharmacy protocol. Samples of radiopharmaceuticals were tested using instant thin- layer chromatography testing to determine the radiochemical purity of the final compounded sterile preparation at t = 0, t = 6, t = 12, and t = 24 hours post compounding. Data submitted was summarized and divided into activity ranges allowing for calculation of average radiochemical purity for various activity levels at each of the four time points. Data was presented in graph form showing the average radiochemical purity values versus time with inclusion of error bars to indicate standard deviation data. The stability of each kit at different activity levels and at different time points post compounding showed that many of the radiopharmaceutical kits prepared today may have an unacceptable decrease in radiochemical purity at higher activity levels and at extended times post compounding. The data submitted provides a general guideline for the stability of radiopharmaceuticals compounded outside of manufacturer guidelines and can be used as a tool to support the practices that are being carried out at individual institutions. However, this data should be used in conjunction with in-house data review to assure that the preparations being compounded and dispensed are of the highest quality for administration to the patient.