The congruence between mothers' and teachers' ratings of mastery motivation among 3-year-old children with mental retardation was investigated. The extent to which maternal and teacher ratings of task persistence at entry to preschool are predictive of observed mastery behaviors at age 5 was tested. Results indicate that mothers rated their children's task persistence behaviors higher than did teachers. Further, once the child's cognitive level and teacher ratings were controlled for statistically, maternal ratings of the child's mastery behaviors were predictive of the child's task mastery performance 2 years subsequent. Implications for educational planning were discussed.