Lifestyle-related disease, which is caused by modifiable factors such as inappropriate diet, physical inactivity, smoking, etc., is a serious problem in Japan. Recently the mortality from lifestyle-related diseases accounted for almost 60% of all mortality, and the medical cost accounted for almost 30% of the total 1) . The workplace has been recognized as an important target for health promotion, as 57.9% of the total population aged 15 yr or over was employed in Japan 2) .In Japan, health education for prevention or management of lifestyle-related diseases at the workplace has been carried out mostly by face-to-face methods such as counselling, and previous studies have shown that these were effective on employees' health [3][4][5][6] . However, the face-to-face approach has some problems in terms of manpower limitations, convenience of employees, and character of employees who prefer not to participate in faceto-face education. One solution to these problems is for support staff to use a non face-to-face approach to employees by means of ordinary mail 7) , telephone, fax 8) , Abstract: To examine the effectiveness of a computer-tailored support tool for lifestyle modification developed for employees, we conducted an intervention study of pre-post test design. The program was based on principles of behavior science referring to goal setting processes, self monitoring, and feedback. The program of the support process was fully automated. A total of 650 participants of four workplaces in Japan completed the baseline assessment, 185 (28.5%) of those returned for the post-test assessment 4 months later. There were significant improvements in lifestyle behaviors between baseline and post-test: In men, low energy intake (p<0.01) and exercise frequency (p<0.05), and in women, low salt intake (p<0.05) and exercise frequency (p<0.05). Furthermore, significant improvements were shown in the stage of change between baseline and post-test: Low salt intake (p<0.01) and regular exercise in men (p<0.01). Our results suggest a possibility that the program, utilizing a computer-tailored lifestyle modification support tool developed for use by employees, had a positive effect on participants' lifestyle behaviors in Japanese workplaces. The degree to which our results generalize to effects of the program is unclear but examination to develop more efficient and effective programs is warranted.