Objective:The study aimed to determine the level of knowledge and the sources of information about normal puberty and menstrual patterns in Turkish schoolgirls from İstanbul.Methods:The study sample was comprised of 922 randomly chosen schoolgirls. A questionnaire survey of knowledge of normal pubertal development and menstrual patterns was conducted.Results:The age of the girls ranged between 10 and 17 years and 82.3% had had menarche. The leading source of pubertal information was the mothers (84.2%). There was no statistically significant relationship between the mothers’ education level and the level of knowledge of the students about pubertal development (p>0.05). The main source for 18% of students was their teacher, but only 6% had a preference for their teacher providing education on this topic. Students who attained menarche preferred education about puberty to be given by health professionals and to both genders at the same setting (p<0.01). A total of 31.5% of students thought that the first symptom of puberty was acne. Half (50.7%) of the students did not know the time period between the beginning of puberty and menarche. The girls who had attained menarche were more knowledgeable about puberty, largely through their own experience.Conclusion:This study shows that schoolgirls have an insufficient level of knowledge about normal puberty. Education programs must be conducted for students and their parents.