This report presents pilot-test results for a science professional development program featuring online, on-demand materials developed by the National Science Teachers Association. During the spring 2006 semester, 45 middle school teachers from three different school districts across the United States participated in a professional development program designed to facilitate content knowledge and skills in the area of Newtonian force and motion. Participants from one of the school districts experienced a full-day instructor-led workshop along with two web-based seminars with a content-area expert. This was followed by a 4-week period of time in which they had access to self-directed, online, on-demand instructional materials that included activities, information, simulations, examples, and practice with immediate feedback over the targeted outcomes. Participants from the two other school districts only had access to the online materials with no instructor-led experience. This report documents positive gains in achievement as well as levels of confidence in teaching the material within all of the professional development groups. Data about the use of specific features within the online material are included, as well as completion rates and attitude survey results. Recommendations for future study are also included.