This investigation evaluated the effectiveness of a 3-year project on the teaching of sex education, funded through Title III of the Elementary-Secondary Education Act. The sample included 515 teachers and 1,110 pupils. Teachers and pupils were assigned according to experimental and control conditions. The experimental group of teachers received special in-service training in the teaching of healthy sexuality. In comparing experimental and control group teachers, the findings indicated no significant changes in general teacher personality characteristics; however, they did indicate that special in-service training did bring about significant changes (increases) in the experimental group teachers' knowledge of and attitudes towards teaching sex education. Also, significant differences (increases) were found in the knowledge of healthy sexuality gained by pupils of experimental group teachers, as compared with pupils of control group teachers. (Author/JA)