Background: Many children and adolescents are physically inactive and become even less active as they age. USA high school students' rates of attendance in physical education (PE) classes sharply decline by grade with 73% of ninth graders attending PE, while only 31% of seniors attend. Non-Caucasian youth report the lowest levels of physical activity participation. Thus, helping teachers to learn how to increase their students' PA during PE is important. Purpose: The purpose of this study was to examine the influences of professional development on teachers' self-efficacy towards teaching physically active fitness and health promoting lessons. Participants and setting: Fifty elementary physical education teachers from a large urban school district in the Midwest USA participated. Thirty teachers volunteered to be in one of the two professional development groups (n = 15 each) with a control group of 20 teachers. Teachers' students were some of the heaviest in the USA with 37% regarded as overweight and 64% reporting spending less than 10 minutes being active in physical education. Intervention: All teachers (n = 30) in the two professional development groups learned how to teach a physical activity oriented curriculum titled the Exemplary Physical Education Curriculum (EPEC) during an eight-hour workshop. Group 1 teachers (n = 15) also participated in two more eight-hour workshops and received two school site visits by teachers experienced in teaching EPEC. Thus, the Group 1 professional development intervention was an extended version of the one-day workshop experienced by Group 2 teachers. Data collection: All teachers (n = 50) in all three groups completed EPEC efficacy and general educational efficacy scales at the beginning (Time 1) and end of the academic year (Time 4). In addition the two professional development groups completed all scales at the start of the first workshop (Time 2) and immediately after the workshop ended (Time 3). Data analysis: Two sets of Repeated Measures Multivariate Analyses of Variance (RM-MANOVA) were conducted. The first RM-MANOVA used scores at Times 1 and 4 for all three groups whereas the second RM-MANOVA was conducted using Group 1 and Group 2 data from Times 1, 2, 3 and 4. Findings: Both intervention groups had increases in their efficacy to teach motor skill objectives (F(1, 28) = 7.26, p less than 0.01, n = 0.21), physical activity and fitness knowledge objectives (F(1, 28)= 8.50, p less than 0.01, n = 0.23), personal and social objectives (F(1, 28) = 3.29, p less than 0.08, n = 0.11) and community efficacy (F(1, 28) = 3.08, p less than 0.09, n = 0.10). Teachers in both groups maintained disciplinary efficacy (F(2, 47) = 4.29, p = 0.02, n = 0.35), whereas the control group suffered a loss of disciplinary efficacy. Associated effect sizes were moderate to large. Conclusions: In general we found support for the value of professional development training in a physical activity curriculum on teachers' self-efficacy perceptions for teaching the curriculum. (Contains 1 table.)