Bayesian statistical analysis is powerful, yet it is infrequently used in many scientific domains. Calculating Bayesian probability distributions is complicated, and available computer programs designed to do the job are slow and inefficient. As a result, a useful intellectual tool for the scientific analysis of data lies largely untapped. This grant supports development of Stan, a powerful, open source computing platform designed by Columbia University statistician Andrew Gelman that calculates Bayesian probabilities quickly and efficiently. Funds from this grant will support Gelman’s efforts to build out the capabilities of Stan, allowing it to seamlessly interact with other computing platforms like R, Python, and Julia that see wide use in the scientific community. Additional funds support development of Stan’s technical capabilities, allowing it to efficiently handle certain complex statistical models and community development and outreach through the organization of conferences and online users groups.