Although the benefits of physical activity (PA) have been well-documented, there is lack of empirical evidence related to the development and delivery of PA motivational programs toward under-representative populations who mainly lead inactive lifestyles such as people with disabilities. The current literature recommends theory-driven and appealing PA intervention programs such as those utilizing advanced technology. Therefore, the purpose of this study was to utilize the psychosocial constructs of the Transtheoretical Model such as social support, successful experiences, and goal setting to develop and deliver web-based PA motivational materials tailored to mainly inactive adults with physical disabilities. This was a true experimental design with two experimental and one control groups. Each of the experimental groups received a 4-week PA motivational program with a different lesson plan for each week. One of the experimental groups (i.e., interactive group) had the opportunity to participate in the website's discussion board, while the other experimental group (web only group) did not. From the 151 individuals who entered the study, 75 (M age = 39 years; Females = 72%; Caucasian = 89%) filled out both the pretest and posttest questionnaires. Participants' PA (Washburn et al., 2002) and stages of change (SOC) (Reed et al., 1997) levels were measured before and after the intervention. A 3 x 2 (group x time) mixed design repeated measures ANOVA revealed a significant time x treatment interaction for leisure-time PA in the web only group (F (2, 72) = 3.3, p = .04). On the contrary, the control group decreased their leisure-time PA level between pretest and posttest (Effect Size (ES) = -.30). Similarly, statistical significance was approached for total PA scores (F (2, 72) = 2.8, p = .07) in the web only group (ES = .34) from pre- to post-intervention. The interactive group had a small increase in both leisure-time (ES = .14) and total (ES = .20) PA. Lastly, Chi-square analyses revealed that the proportion of people in the web only group (59%) who progressed in their SOC was higher than the proportion that progressed in the control group (27.6%) (¥ö2 [1, N = 51] = 5.13, p = .02). These findings support the efficacy of the web-based materials on PA behavior change. Future PA promotional projects can utilize advanced technology (e.g., expert systems design) and expanded intervention programs for PA behavior change within under-representative and ethnically diverse disability populations. Funded by NIDRR, USDE. Keyword(s): health promotion, physical activity, research