Background: Millions of American children are participating in fitness testing in school-based physical education (PE) programs. However, practitioners and researchers in the field of PE have questioned the need for regular or mandatory youth fitness testing. This was partly because a significant improvement in youth fitness and physical activity (PA) levels has not been demonstrated since the implementation of such tests in the 1950s. Therefore, there is a need to understand fully the role of youth fitness testing in school-based PE programs. Purposes: Given that no data are available to enrich our understanding of the determinants of teacher use of youth fitness tests in PE programs in the USA, this study aimed to identify variables that influence teachers' use of fitness tests, guided by the theoretical model of Ronis, Yates, and Kirscht for determinants of a repeated behavior (i.e., use of fitness tests in this study). Participants: Full-time PE teachers (n = 325) from 10 states in the USA participated in the study. The average age of the participants was 40.17 years (SD = 10.7). The average elementary and secondary teaching experiences were 6.6 years (SD = 8.5), and 8.2 years (SD = 10.3), respectively. There were 177 (54.6%) females and 146 (45.1%) males. In total, 83% of the participants used various fitness tests. Data collection: The researchers generated an initial survey, guided by survey research theories due to the lack of a pre-validated instrument. The theoretical model of Ronis, Yates and Kirscht, which consisted of three major factors: unreasoned influences, resources or enabling variables, and reasoned influences, provided guidance for the selection of primary factors, the sub-factors in each factor, and items in each sub-factor. The survey was pilot tested through multiple phases to ensure acceptable score reliability and validity. Three approaches were employed to collect the data. First, some surveys were mailed to teachers that the investigators knew directly. Second, PE teacher educators in different states were asked to mail materials to teachers they knew. And third, a PE email list was used to solicit participants. In total, 821 surveys were distributed and 325 were usable. The actual return rate was difficult to determine because some teacher educators failed to record the number of surveys they sent out. Data analysis: The means and standard deviations for each of the three factors in the model of Ronis, Yates and Kirscht were calculated. Negatively worded items were reverse-coded to be consistent with the scoring of the positive items. The higher the score, the stronger the endorsement of the statement/item. Discriminant function (DF) analysis was performed multiple times using different combinations of data sets to explore the determinants thoroughly. Results: The results of the DF analysis suggested that reasoned influence (i.e., intentions of using fitness tests for students, perceived benefits, perceived self-efficacy, and overall attitudes) and resource enabling factors were found to predict if teachers implement fitness tests. No demographic variables were identified as determinants when analyzed with other variables. Conclusions: The results from this study confirmed that there were various determinants of teacher fitness test use and the model of Ronis, Yates and Kirscht could guide the investigation of the repeated behavior--teacher use of youth fitness tests. Among the three factors in the model, reasoned influences and resource enabling factors were the determinants, suggesting test promoters may need to take into consideration those factors when revising the nationally available fitness tests. The data also provided empirical evidence to support the need for youth fitness testing from the teacher perspective. (Contains 1 figure and 5 tables.)