Mastery motivation, usually measured by task persistence, is often used to predict infant competence. This study attempted to clarify how a measure of persistence can be used to facilitate the prediction of competence when examining the relationship between persistence and maternal child-rearing behavior. The measure of persistence used in this study incorporated several qualitative aspects of persistence, such as multiple problem solving strategies. When they were approximately 18 months old, 31 children were videotaped while they performed various problem-solving and exploratory tasks. Children's problem solving was rated on scales that measured persistence, affect, and task performance. Children also completed the Bayley Scales of Mental and Motor Development. The HOME Inventory was used to rate aspects of the child-rearing environment. Results indicated that persistence was related to aspects of the child-rearing environment; levels of persistence were related to total scores on the HOME inventory. Results suggested that persistence best facilitates competence when a task is very difficult or challenging for a child, and that qualitative aspects of persistence have a stronger association with aspects of the child-rearing environment than do quantitative aspects such as attention span. (MM)