This paper reports the formative evaluation of six curriculum units related to initial number sentence writing. These units were used for a coordinated study carried out by the Mathematics Work Group of the Wisconsin Research and Development Center for Individualized Schooling. The units were tried during the 1977-78 and 1978-79 school years at a single elementary school located in Madison, Wisconsin. Information, including in-class observation, reports from teachers, pupil assessment, and notes from pupil comments, was gathered from trying the materials on about 50 children through their first and second years of elementary school. The information is summarized by topic or unit and suggested revisions are stated. Copies of the newly developed units are contained in the Appendix to the report. (Author/MK)