In this research, a system was developed to enable underlining by learners to promote reading comprehension of e-learning instructional materials, and an attempt was made to further promote such underlining activity by evaluating and providing feedback on the learner's underlining. E-learning instructional materials implementing this feature were created and used as auxiliary instructional materials in actual classes, and a group of learners using instructional materials with underlining capability only were compared against a group of learners using instructional materials which also provided the feedback feature. The following results were obtained for the latter group: (1) The usage rate of the instructional materials was higher, (2) Underlining activities thought to be desirable for reading comprehension were more frequently seen, and (3) The rate of correct answers on a test for confirming reading comprehension was higher. These results suggest that the feedback feature for underlining which was implemented in this research is effective for promoting reading comprehension.