A large amount of food waste in known to bring about many problems including environmental pollution. This study was carried out to investigate effective methods for reducing leftovers in the food service business & industry. The reasons for producing leftovers in food service restaurants, customers perferences of foods, cooking methods the degree of saltiness, and serving size were surveyed using questionnaire and the menu was improved based on the customers perferences. Excessively large serving sizes and the unfavorable cooking methods is food service were the main reason for the leftovers of side dish and one=dish foods. Because the largest amount of leftover came from soups & stews, an effective way of reducing leftovers in food service would be to reduce the serving size of soups & stews. Total leftovers was reduced to about 60% after improving menu (p<0.01) and the each leftover or rice, soup&stew, and side dishes was also reduced significantly after improving the menu(p<0.001) The environmental campaign to reduced food waste by bulletin intra-net using personal computers slogans& posters, and new letters was conducted for one week each and then leftovers were measured 9 times for following three weeks regularly. The total amount of leftovers decreased slightly due to the environmental campaign, but the difference was not significant . When we adopted penalty or prize system leftovers were decreased by about 35%(p<0.001) and the penalty system was more effective than the prize system in reducing leftover (p<0.001) When we compared the leftovers under the three services, a tray service was more effective in reducing leftover than complete self-service of partial self-service(p<0.001).