This 20-year longitudinal study was undertaken to trace developmental changes in children's moral reasoning. Initial data collection (Time 0) was begun in 1955-1956, with interviews conducted every three to four years thereafter. Sixty of the 96 participants were interviewed at least twice. The original sample consisted of 72 boys selected from two Chicago suburbs. The group was equally divided among three age groups (10-, 13-, and 16-year-olds), two social classes (middle and working class), and those high and low in sociometric popularity. The first wave of data collection also included a comparison group of 12 delinquent boys. Twelve auxiliary participants were later added to the sample. All participants received the nine dilemmas of Kohlberg's moral judgment interview. Additional questions tapped independence of judgment, comprehension, identifications/exemplars, and moral ideals. Most of the interviews included questions on the ideal self, occupational aspirations, family background, and life experiences, as well as two Q-sorts: a Social Respect Sort, ranking the respect accorded to different occupational roles; and a Be-Like Sort, ranking how much the subject wanted to be like people in various personal and occupational roles. Other measures, by wave, are as follows. TIME O (1956): socioeconomic status (Hollingshead), sociometric status (Moreno, 1944), 10 scores (Kuhler-Anderson text), roleplaying. TIME A (1960): teachers' ratings, parents' data (moral judgment interviews and measures of child rearing attitudes and practices). TIME B (1964): Thematic Apperception Test (TAT) stories. TIME C (1969): five-point scale of attitudes toward sex. TIME D (1973): occupational rating scale. TIME E (1977): cognitive measures/formal operations problems, measures of interpersonal role-taking, job and family descriptions, life outcomes questionnaire. TIMES C, D, and E: metaethical questions, reconstruction (interpretations of past responses and/or logical reconstructions of moral arguments), Loevinger Sentence Completion Test. Raw data and computer-accessible data are available.