The purpose of this research was to understand fifth grade children's cognitive behavior as they wrote, solved and then, in small groups, shared original math story problems. Research questions examined children's: (1) beliefs about math in this problem-writing classroom, (2) math story problem-writing behavior, (3) difficulties with their self-generated problems, and (4) small-group problem solving behavior. Case studies were conducted in the context of a teaching experiment in one fifth grade classroom. Children were engaged to write, solve and then share math story problems three or four days a week during this one year study. There were three overlapping groups of participant children. Eight children were observed as they wrote and solved math story problems. Seventeen children, including the eight previously observed, were observed via audio-recordings as they shared story problems in small groups. The entire class of 25 children was interviewed or surveyed regarding their math-related beliefs. The findings indicate that these children tended to express problem-oriented and holistic beliefs about mathematics. Children showed a variety of planning behaviors during problem writing. Generally, children composed problems that they themselves had difficulty understanding or solving. Finally, children were extremely task-focused when sharing peer-generated problems in small groups. The outcome of small-group sessions was being shared. It was concluded that children's problem writing and solving behavior reflected the expectations and beliefs of this school math literacy community. The principal implication of this research for teachers is that children's original math story problems provide one important alternative source to textbook and teacher-generated math problems. Further research on the relationship between problem ownership and problem solving behavior is recommended. (49 references) (Author/MDH)