Research in moral development from a cognitive-developmental model has been greatly influenced by the Piagetian stage theory of Lawrence Kohlberg. Based on the assumption of inherent cognitive development of internal structures, Kohlberg's theory maintains that the stages are universal across cultures and persons. As a primarily organismic theory, minimal importance is given to external factors such as culture, socialization processes, and situational context. Individuals are expected to progress sequentially through each stage regardless of cultural, personal, or environmental influences. The primary instrument used in assessing moral development in the literature on Kohlberg's theory is the Moral Judgment Interview (MJI) originally developed in Kohlberg's (1958) doctoral dissertation. In general, the empirical evidence provides little support for Kohlberg's assertion of a strict stage concept. Despite a moderately high level of consistency using the MJI, which may be related to instrument bias, the longitudinal data exhibit significant inconsistencies that cannot sustain the "structured whole" assumption. There appears to be significant support for upward sequentiality through Kohlberg's stages, with qualifications. First, the strength of this evidence rests on extensive revisions to the scoring systems which have eliminated deviant findings of regression and stage-skipping. Second, the evidence that does support the notion that the upward sequentiality assumption is limited to the lower stages of Kohlberg's hierarchy. Kohlberg's research program has encountered substantial problems in supporting the empirical existence of principled Post-Conventional reasoning. (LLL)