This study examined the reliability and validity and hypothesized factor structure of two assessments of self-determination, the Arc’s Self-Determination Scale (SDS) and the American Institutes for Research Self-Determination Scale (AIR) in students with autism spectrum disorders (ASD). Ninety-five middle and high school students (17% female and 83% male) aged 13 through 21 years participated. Item analysis and confirmatory factor analysis were conducted separately for the SDS and AIR data. Together, the findings of this study suggest that (a) the two measures in this study show reliability and validity in the measurement of global self-determination in students with ASD and (b) the parameter estimates and the model fit statistics support the hypothesized factor structure of both instruments (with light variation for the SDS). Suggestions for future research and implications for educators are discussed.