This study examined what teachers know about health-related fitness (HRF) and how confident they are in their knowledge. Seventy-three middle school physical education teachers completed a 3-part cognitive HRF test and a self-efficacy questionnaire that required responses to statements about how confident they were in passing a HRF knowledge test. Results indicated that teachers were very confident in their knowledge of HRF; however, their actual HRF test scores did not meet the standard of achievement expected of a ninth-grade student as assessed by the South Carolina Physical Education Assessment Program. Further investigation of the influence of teacher characteristics related to HRF knowledge revealed that age and years of teaching experience significantly related to self-efficacy but not to HRF knowledge. This study implies that targeted teacher development is a necessary part of attaining and maintaining HRF knowledge required to teach to state and national standards. Teacher Self-Efficacy Questionnaire (Sample Questions) is appended. (Contains 1 table.)