The purpose of this study was to investigate the effectiveness of two experimental methods of teaching the present progressive verb tense based on four instructional principles: teach form-function relations, compare similar grammatical forms, promote learner autonomy, and provide opportunities for generative use. Ninety-nine Japanese first-year high school students participated in the study. A 3 (groups) x 1 (test) Analysis of Variance procedure revealed no statistical differences among the three groups at the beginning of the study; however, both an immediate and a delayed post-test showed statistically significant differences between the control group and the two experimental groups (p less than 0.001). The findings support the idea that a communicative grammar explanation coupled with structure-based communicative tasks designed around specific instructional principles constitutes one effective approach to grammar instruction. (Contains 2 tables.)