This study examines amodification of the iterative model (Rittle-Johnson & Siegler, 1998), in which metastrategic knowledge was hypothesized to be a mediator underlying the relationship between conceptual and procedural knowledge. Fifty=six fith-graders participated in this study. The children solved fraction problems, half of which were computation problems and half of which were work problems. Two approaches were used to assess conceptual and procedural knowledge: the same-problem approach and the different-problem approach. Both approaches yielded similar findings. Conceptual, procedural, and metastrategic knowledge correlated positively with each other. The correlation between conceptual and procedural knowledge was reduced after controlling for metastrategic knowledge, suggesting that metastrategic knowledge played a role in the relationship between conceptual and procedural knowledge. The relationships among the three knowledge types grew stronger over trials, indicating developing link among them.