With the increased workplace demand for STEM specialists, and the trend in capable students opting out of higher levels of secondary mathematics, the psychological influences on mathematics subject choice are important issues to explore. Expectancy-value theory is used to examine the factors influencing such achievement choices. In the present study, as part of a larger programme of research on mathematics subject choice, we sought to validate self-report measures of students' expectancies for success, values, and perceived costs associated with participation in mathematics. Confirmatory factor analysis supported the hypothesised factor structure, with the measures displaying acceptable levels of internal consistency.