Predictive stability studies allow the long-term stability characteristics of a drug substance or drug product to be characterized from extrapolation of results from a short-term stressed stability study. These studies are typically one month in duration and focus on chemical degradation. This chapter focuses on accelerated stability assessment program (ASAP) studies as one method of predicting stability. The main phases of performing an ASAP study are described including designing the protocol, setting down the studies, storing and analyzing the samples followed by reviewing and modeling the data and performing predictions. The applications of predictive stability studies are also discussed including in regulatory submissions.