In the present study, the reliability and construct validity of the Japanese version of the Chalder Fatigue Scale was evaluated as a measure of severity of fatigue among young students in Japan. A healthy group comprised 27 Grade 6 primary school students and 28 Grade 1 junior high school students. The severely fatigued group were hospital outpatients with childhood chronic fatigue syndrome (n = 21). Principal components analysis with varimax rotation identified 4 factors which accounted for 63.2% of the total variance, as in the original English version. Internal consistency (Cronbach coefficient α) was .73, and test-retest reliability measured using Spearman rank correlation coefficient was .55. Scale scores of the healthy subjects were lower than those of the patients with childhood chronic fatigue syndrome. The reliability (a) and construct validity of the Japanese version of the scale among healthy students in Japan were satisfactory for research studies among healthy school students.