Schumacher and Nash (1991) theorize that writing provides an avenue for people to reorganize their knowledge. Kieren (1988) is one of several researchers who theorize that children's school fraction experiences should begin with personal knowledge of fractions. The purpose of this study was to determine whether or not children who engaged in journal writing about fractional situations showed an increase in fraction knowledge. Two groups of fourth-grade children at a large, Southwestern United States, urban elementary school participated in the study. One group completed a four-week intermittent writing experiment. The other group had no such experience. The results of this study indicated a significant difference between pre- and post-test scores for the writing group children. The results add evidence to the theory that writing causes learning and call teachers to provide writing situations associated with children's existing informal knowledge of fractions. (Contains 35 references.) (Author/ASK)