This chapter discusses the definition and historical background of gain-based damages. The normative bases of gain-based relief are explored, particularly the controversy over whether the account of profits is deterrent. The call for the extension of availability of gain-based damages to common law causes of action is discussed. The vexed position of ‘reasonable fee’ awards is canvassed, including whether these awards properly belong in the gain-based family. Finally, the issues of causation and remoteness, and the availability of allowances for skill and effort are covered. There remain areas of great uncertainty and confusion, particularly in regard to the normative basis for disgorgement, the extent to which gain-based damages have been or should be extended to common law causes of action, and, finally, the nature of and distinction between awards which effect full disgorgement of profits and those which impose only a ‘reasonable fee’.