The meaningfulness of psychotherapy outcome as measured in therapy research is a persistent and important issue. Following a period of emphasis on statistically significant findings for treated versus control groups, many researchers are renewing efforts to investigate the meaningfulness of individual change. Several statistical methods are available to evaluate the meaningfulness of client's changes occurring as a result of treatment. This article reviews the history of the clinical significance concept; describes the various methods for defining improvement, recovery, and clinically significant change; examines current criticisms of the methods; and describes the current use of the methods in practice.