This longitudinal study investigated how girls and boys who were discrepant in their spatial and verbal performance used spatial visualization skills in solving word problems and fraction problems. The subjects, 36 girls and 33 boys, were interviewed annually in Grades 6, 7, and 8. Each student was asked to read a problem, draw a picture to help solve it, solve it, and then explain how the picture was used in the solution. Students who differed in spatial visualization skill did not differ in their ability to find correct problem solutions, but students with a higher level of spatial visualization skill tended to use spatial skills in problem solving more often than students with a lower level of skill. Girls tended to use pictures more during problem solving than boys did, but this did not enable them to get as many correct solutions. Low spatial visualization skill may be more debilitating to girls' mathematical problem solving than to boys'.