The purpose of this experimental study was to explore the instructional effectiveness of integrating varied instructor-provided concept maps into an online hypertext learning environment, and the effect of learners' self-directed learning abilities on their learning performance. The research adopted a randomized posttest with two-control-group design. Two major instructional treatments were traditional and interactive concept maps embedded in the online hypertext material. One hundred twenty-six undergraduate students from a public university in the U.S. participated in the study. Student participants were segregated into two levels of self-directed learning groups. Three criterion tests, including identification, terminology, and comprehension tests, were used to measure students' learning performance. Results indicated that (a) the interactive concept map was superior to the traditional concept map in facilitating students' knowledge acquisition, (b) students' self-directed learning abilities did not influence their learning performance, and (c) the concept mapping strategy did not increase students' self-directed learning abilities.