Depression during adolescence is highly prevalent with as many as 20% experiencing a major depressive episode by the age of 18. Adolescent depression causes significant impairment across life areas including school functioning, such as poor academic performance and decreased academic achievement. Despite the existence of many evidence-based treatment options, merely 25% of depressed adolescents receive treatment. For this reason, it is essential that easily accessible preventive interventions for adolescent depression be developed and made available. Computerized interventions could broaden the reach of prevention efforts and preliminary results indicate that they have the potential to successfully prevent adolescent depression. The Coping with Depression course is an empirically validated cognitive-behavioral depression treatment and prevention program that is well-suited for computerized delivery. This dissertation reports on the development and evaluation of a web-based interactive multimedia version of the adolescent Coping with Depression course with students experiencing subclinical levels of depression. The Blues Blaster program includes the following six modules, with five mini-sessions in each: (a) defining depression, (b) mood monitoring, (c) increasing fun activities, (d) increasing positive thinking, (e) recognizing negative thinking, and (f) decreasing negative thinking. Key concepts are presented and reinforced in a variety of engaging ways within each session, including video, animation, comic strips, graphics, interactive exercises, and games. The Blues Blaster program was evaluated in a randomized controlled trial with 161 adolescents who were randomly assigned to either the Blues Blaster or information-only control conditions. Participants were assessed at baseline, post-treatment (six weeks after baseline), and six-month follow-up. Results demonstrated greater improvement for the Blues Blaster condition in depression levels, negative thoughts, behavioral activation, knowledge, self-efficacy, and school functioning compared to the information-only control condition. These findings suggest that this targeted prevention program is appropriate for use with middle school students to decrease depression levels and therefore the risk that they will develop major depression in the future. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]