The analysis of adverse event frequency from clinical development projects includes summarization of important features of the occurrence of adverse events such as how often they occur, when they emerge, how often they recur, and how severely they are manifested. Comparisons of risks among treatment groups are essential for this evaluation, particularly as expressed by confidence or credible intervals for measures of difference between or relative risk of adverse event occurrences among treatment groups. This chapter describes some means for summarizing and getting an understanding of the adverse event profile of the treatments in clinical development programs, most usually clinical trials. Typical examples include survival-type analysis for adverse event emergence and recurrence, and various regression modeling strategies for identifying potential predictors of adverse event occurrence other than assigned treatment. The chapter describes a Bayesian screening method that adjusts for the potential multiplicity issue that arises when many events occur.