Adaptive enrichment designs involve preplanned rules for modifying enrollment criteria based on accrued data. They involve multiple populations of interest, e.g., defined in terms of a biomarker or risk score measured at baseline. This module will present methods and software for the design and analysis of adaptive enrichment designs. It will also present methods for improving precision of estimators of the average treatment effect, by leveraging information in baseline variables; these methods can be used in adaptive designs as well as non-adaptive trial designs.