This action research project describes a program for improving student comprehension of mathematical vocabulary. The targeted population consisted of two classes of fifth grade students from two elementary schools located in the suburbs of a large metropolitan area in Illinois. The problem of poor mathematical vocabulary was documented through teacher and student surveys and questionnaires, student vocabulary checklists, and teacher observation of students' daily work. Upon analysis of the data with respect to probable causes, it was discovered that students have varied mathematical backgrounds, suffer from math anxiety, and have poor reading comprehension. In addition, expectations of students have shifted due to a change in standards by the National Council of Teachers of Mathematics (NCTM) and on the Illinois Standards Achievement Test (ISAT). Furthermore, it was revealed that the vast majority of math series focus on computational facts rather than mathematical vocabulary. A review of solution strategies proposed by experts in the field, combined with an analysis of the problem setting, led to the following interventions: student math journals, student-created math dictionaries, children's literature to introduce and reinforce mathematical concepts, graphic organizers, visual aids, and written explanations of open-ended word problems. As a result of the aforementioned interventions, the students exhibited an increase in comprehension and use of mathematical vocabulary in math performance and in communication of mathematical ideas. (Contains 45 references.) (Author/ASK)