This chapter examines several aspects of mastery motivation in 3-year-old children with Down syndrome. It extends to which distal and proximal aspects of children's early care-giving environment were associated with their subsequent mastery motivation. The assessments performed after 1 year of age showed stronger and more consistent relations with later mastery motivation. Cognitive performance correlated with later persistence on both tasks, and with affect and competence on the puzzle tasks. Adaptive behaviour correlated with persistence on the cause-and-effect tasks and with competence on both tasks. Independent play showed consistent negative relations with simple exploration on both tasks; children who demonstrated higher levels of independent play at 1 year of age displayed less simple exploration on mastery motivation tasks at 3 years of age. The two measures of the proximal care-giving environment revealed different patterns of relations. The provision of play materials was positively related to higher levels of persistence and competence on the puzzle tasks.