The Korean National Commission for Unesco has helped Korean Unesco Associated Schools undertake environmental studies within the framework of education for international understanding, cooperation and peace from 1991 - 1993. The environmental studies enjoyed participation by nine Associated Schools among 35 throughout the country, with each school on a different theme each year. Environmental studies by the Unesco Associated Schools are differentiated from those by the former continues to work on environmental or Provincial Boards of Education. The former continues to work on environmental education, longer than 1 - 2 years, and they can also capitalize on the international networks of the ASP, which may be instrumental to understanding the worldwide nature of the environmental issues these days. This paper contains a breif explanation of the cases of environmental studies by level of education from primary to teacher education level. It is argued that through the study, the students of Unesco Associated Schools well recognize the seriousness of environmental problems facing mankind and will have positive attitudes and values towards the preservation of our environment. It is also argued that the studies result in a variety of useful teaching/learning methods for environmental education: students visit to polluted areas. survey, composition of works with environmental themes such as posters, poems, organization of discussion by the students on environmental problems, exhibition, international correspondence, etc. The studies also have produced various helpful reaching/learning materials : photos, slides, scrapbooks of articles on environmental issues from newspapers, etc. However, several problems also emerged through the studies. A few of them are described here ; First, focus on the extra-curricula activity rather than regular curricula results in the neglect of the knowledge base of environmental education. Second, only a part of the all 35 Associated Schools have participated in the project. Third, primary and first secondary students have difficulty in using foreign language which is vital for international activities.