The small sample power and the probability of a Type I error of a permutation test were investigated for the two‐sample problem. Empirical probabilities were obtained under the null and various alternative conditions for the permutationt‐test and, for comparison, Student'st‐test and the Mann‐Whitney 17‐test for normal, uniform and skewed populations. Values of the empirical α were within sampling variation bounds of the theoretical α, and the power values for the permutationt‐test were generally close to those of Student'st‐test and the theoretical values. For the skewed population, the power values of the permutationt‐test were higher than those of Student'st‐test if the means were positively related