This study examined relations between internalization of conduct rules and the temperamental quality of inhibitory control in 103 children followed from toddlerhood to early school age; and used recent methodological suggestions to obtain better estimates of stability to examine longitudinal continuity of internalization. Maternal reports of children's inhibitory control were collected at ages 2.5, 4, and 6 years using the Child Behavior Questionnaire. Children's internalization was observed at ages 4, 5, and 6 years in 3-minute videotaped game-playing situations that provided the children an opportunity to violate (cheating at a game) or comply with rules while unsupervised. An overall internalization composite score for each time of assessment was comprised of three composite scores: (1) mean latency to transgress; (2) mean extent of transgression; and (3) mean extent of rule-compatible behavior. Results indicated that inhibitory control at age 2.5 predicted internalization when children were 4 years old, but not when they were 5 and 6 years old. Inhibitory control, however, was associated with internalization concurrently at ages 4 and 6 years. Internalization was modestly stable across times of assessment. (Contains 16 references.) (Author/KB)