Purpose: To suggest ideas that promote sexual health and useful in planning sex education programs for middle school students. Method: This study surveyed 661 middle school students from three schools in Seoul and Chunchon. Result: The average degree of sexual knowledge was 31.5, while attitude was 32.5. There were statistically significant differences in sexual knowledge in relation to: coeducational environment (t=-5.776, p=.000), grade (F=36.351, p=.000), father's age (t=-2.510, p=.012), mother's age (t=-2.146, p=.032), economical status (F=3.264, p=.039), source of sexual knowledge (F=8.484, p=.000), the degree of interest in the opposite sex (F=16.871, p=.000), sexual discussions with parents (t=3.556, p=.000), sexual discussions with teachers (t=2.847, p=.005), and sex education (t=2.148, p=.032). Likewise, stastically significant differences in sexual attitudes were linked to: coeducational environment (t=-7.646, p=.000), subject's grade (F=32.743, p=.000), parental marriage status (t=2.338, p=.020), mother's age (t=-2.048, p=.041), source of sexual knowledge (F=6.917, p=.000), the degree of interest in the opposite sex (F=15.559, p=.000), sexual discussions with parents (t=3.908, p=.000), and sexual discussions with teachers (t=2.946, p=.003). The students level of sexual knowledge and attitude was significantly correlated (r=.686, p=.000). Conclusion: This study indicates a variety of systematic sexual education programs are needed for middle school student at home and school.