This paper tested relations between two measures of mental toughness. A sample of 110 male athletes (M age = 20.81. years, SD = 2.76), derived from University sports teams and local sports clubs, gave informed consent before completing two questionnaires to assess mental toughness. It was hypothesized that scales and subscales from the two different instruments, which purported to measure the same or substantially overlapping scales, would be strongly correlated. Predictions concerning the expected relations were made a priori. Pearson correlations revealed a significant and positive relationship between higher order mental toughness scores (r= .75; p< .001). Correlations between similar mental toughness subscales were found to be positive and significant but somewhat lower than expected (r= .49-62). Results suggest instrument subscales with similar labels are not measuring the same components of mental toughness. 2010 Elsevier Ltd.