 The results of this study suggest that the Japanese version of the tolerance of ambiguity in medical students and doctors, J. Tamsad, scale, is a reliable and valid measure of ambiguity tolerance in medical trainees in Japan. This scale may be useful for assessing ambiguity tolerance among medical trainees in Japan, as well as for evaluating the educational effectiveness of curricula that foster ambiguity tolerance in medical trainees, or even in research assessing the relationship with other variables. This article was authored by Hirohiza Fujikawa, Desuki-san, Mikiohiyoshi, and others.