Duehring, MD, Feldmann, CR, and Ebben, WP. Strength and conditioning practices of United States high school strength and conditioning coaches. J Strength Cond Res 23(8): 2188-2203, 2009-This study describes the results of a survey of the practices of high school strength and conditioning (HS S&C) coaches. Thirty-eight of 128 (29.7%) HS S&C coaches, who were surveyed, responded. This survey examines background information, physical testing, flexibility development, speed development, agility development, plyometrics, strength/power development and program design, nutrition, and injury frequency. High school strength and conditioning coaches average 14.78 years in the profession, and 89% of the survey respondents were certified by the National Strength and Conditioning Association. Coaches assess an average of 5.83 different parameters of fitness, with strength as well as power being the most common parameters assessed. Coaches tested an average of 3.86 times a year with an average of 8.51 specific tests per testing session. All HS S&C coaches used a variety of flexibility development strategies using dynamic stretching more frequently than static. Thirty-six of 38 (95%) coaches follow a periodization model, 37 of 38 (97.4%) coaches indicated that their athletes used Olympic-style lifts, and 37 of 37 (100%) coaches responding to this question used plyometric training with their athletes. The squat and its variations, as well as the Olympic-style lifts and its variations, were most frequently identified as the most important exercises prescribed. All coaches use speed development and agility training strategies with their athletes. This survey examined a variety of other practices and provides detailed information about these practices at the high school level. Coaches are encouraged to review the strength and conditioning practices described in this survey and identify and implement the ideas that may improve their practices.