Presented are four national case studies carried out by the Population Education Section of the United Nations Educational, Scientific, and Cultural Organization (Unesco). Designed to assess the effects of population education programs on the educational process, these research projects focused on El Salvador, The Republic of Korea, Philippines, and Tunisia. Discussed in each case study are the program's organization, objectives, activities, teacher education efforts, research strategies, and characteristics of the country's population. Conclusions address the program's effects upon students, teachers, curricular content, and instructional methodology. (WB)