Oshio T, et al. - Given that educational disparities in incidences of non-communicable diseases (NCDs) are well recognized, researchers addressed this matter using a hazards model analysis, with particular reference to the potential mediating influences of socioeconomic status (SES), other than educational level, and health behaviour as well as sex differences. From a 12-wave longitudinal nationwide survey of middle-aged Japanese, 31,210 subjects (15,127 men and 16,083 women) with age 50–59 years at wave 1 were analyzed in this study. Both men and women exhibited higher incidences of diabetes and stroke in relation to lower educational level. Only among women, a link was evident between lower educational level and hypertension. The range of relative indices of inequality was from 1.37 for stroke among men to 2.65 for diabetes among women, after controlling for baseline SES, health behaviour, and regional areas. In this study, educational level was found to be significant as a predictor of the incidences of selected NCDs, particularly among women. Findings revealed limited mediating impacts of other SES and health behaviour.