The purpose of this study was to test the construct validity and reliability of the Health Self-Determinism Index for Children (HSDI-C), an instrument designed to measure intrinsic motivation in health behavior. An convenience sample of 558,7 to 13 years old children completed the Korean version of HSDI-C. The findings were as follows : 1. Construct validity was supported through factorial isolation of four theory-consistent subscales ; Internal-external cue responsive ness, Self-determinism in health judgement, Competency in health matters, and Self-determinism in health behavior /goal. The total percent of variance explained by 4 factors was 2 percent. 2. The correlations between the four factors were ranged from -.06 to .29 indicating that factors are not redundant and each factor contributes uniquely to the total construct. 3. Cronbach alpha coefficient for internal consistency was .96 for the total, and .72, .56, .69, and .75 on the respective subscales. Test-retest reliability for the total scale was .85 at 2 weeks. 4. The Analysis of variance for the HSDI-C total scale and subscales according to grades revealed that there were significant differences in means for the total and factor one and two, indicating younger children were more extrinsically motivated.