3 theoretical approaches to the origin and development of the infant-mother relationship are reviewed: psychoanalytic theories of object relations, social learning theories of dependency (and attachment), and an ethologically oriented theory of attachment. "Object relations," "dependency," and "attachment," although overlapping, are seen to differ substantially. Among the concepts in regard to which there are significant intertheoretical differences, the following are discussed: genetic "biases," reinforcement as compared with activation and termination of behavioral systems and with feedback, strength o f attachment behavior versus strength of attachment, inner representation of the object, intra-organismic and environmental conditions of behavioral activation, and the role of intra-organismic organization and structure. Finally, the relation between theory and research methods is considered.