Data from 181 college students were used to assess whether math reasoning item response times in computerized testing can provide valid and reliable measures of a speed dimension. The alternate forms reliability of the speed dimension was .85. A two-dimensional structural equation model suggests that the speed dimension is related to the accuracy of speeded responses. Speed factor scores were significantly correlated with performance on the ACT math scale. Results suggest that the speed dimension underlying response times can be reliably measured and that the dimension is related to the accuracy of performance under the pressure of time limits. (Contains 6 tables and 4 figures.)