This study examined the social organization of a problem-solving task among 15 African American and 15 European American sibling pairs. The 30 sibling pairs between the ages of 6 and 12 were video recorded constructing a marble track together during a home visit. African American siblings were observed to collaborate more often than European American siblings who were more likely to divide up the labor and direct each other in constructing the marble track. In addition, older European American siblings made more proposals of step plans than older African American siblings. The findings provide insights into the cultural basis of the social organization of problem solving across African American and European American siblings.