Abstract: Gaviglio, CM and Cook, CJ. Relationship between midweek training measures of testosterone and cortisol concentrations and game outcome in professional rugby union matches. J Strength Cond Res 28(12): 3447–3452, 2014—The aim of this study was to assess the response of salivary-free testosterone and cortisol concentrations across selected midweek skill-based training sessions and their association with subsequent match outcome 3 days later. Twenty-two rugby union players were assessed for salivary-free testosterone and cortisol concentrations before and after a midweek training session over 6 consecutive weeks. The relative percentage change (response) in the testosterone and cortisol concentration and the testosterone to cortisol (T/C) ratio was also determined. Game-day analysis consisted of prematch testosterone concentrations and match outcome. Data were pooled across the winning (n = 3) and losing (n = 3) outcomes. The midweek pretraining T/C ratio was significantly lower (p < 0.01) before a win than a loss and the increase in the pre- to post-T/C ratio before a win was significant (p < 0.001). The increase in the pre- to post-testosterone concentration before a win was also shown to be significant (p < 0.01). However, the relative changes in testosterone before games that were won were not statistically different to that of games lost (p > 0.01). Significant relationships were also demonstrated between game-day pre-testosterone concentrations and the midweek cortisol response (r = −0.90, p = 0.01) and midweek T/C ratio response (r = 0.90, p = 0.01). In conclusion, a midweek measurement of the T/C ratio against a skill-based training session seems to show some potential as an early indicator of subsequent successfully executed performances in competitive rugby union. If this work is subsequently validated, further monitoring of midweek hormone concentrations in response to a mixed psychological-physical training session may assist with assessing competitive readiness leading up to competition.