This study try to understand the effects of an informative lecture on children's pubertal knowledge and self perceptions. The sample was consisted of 524 secondary school students. The students from 6th to 8th grades ranged in age from 10 years 10 months to 15 years 7 months. A series of questions related to pubertal developments and Harter's (1988) Self Perception Profile for Adolescence was used to measure the general pubertal development knowledge and self perceptions of early a dolescents respectively. It was found that male and female adolescents' post-test performance was higher than the pre-test performance in all grade levels except Ab grade boys. Female adolescents obtained significantly higher scores than adolescent males in Ab and 8th grades. GradeXgender interaction for physical apperances also revealed that 7th grade girls and M grade boys are most negative about their physcial apperances. Male and female adolescents' self perceptions about close friendship and "internal self' were very similar before the puberty lecture. However after the lecture male adolescents evaluated their mentioned selves more negatively than female adolescents. It can be concluded that adolescents managed to increase their knowledge base about puberty but the program had some effect on male and female adolescents' self perceptions in different directions.