The paper is a theoretical analysis of the evolution of the concepts related primarily to the definition and to the antecedents of self-injurious behavior (SIB). It was found that the definition of SIB as currently used contains surplus meanings unrelated to its scientific utility. At present, a restricted definition of SIB is not warranted because its basic parameters have not been studied adequately. Analysis of SIB taxonomies suggests two subclasses of SIB: social and nonsocial. Epidemiological studies of SIB suggest chronic and acute subsamples that differ in organicity, chronicity, and length of institutionalization. Ecological analysis suggests that a variety of antecedent conditions affect rates and topographies of SIB, e.g., ambient environmental conditions, background settings, situational demands, self-restraint, and type of daily routine activity. Implications were drawn for the organization of therapeutic environments, the study of covariation among collateral topographies, the dynamics of SIB responding, and sequential dependencies among SIB and related topographies.