Aim of the study: To assess the knowledge, attitude and practice toward menstruation among adolescent girls at Sohag City Methods: A descriptive cross-sectional design was utilized for the study. A convenient sample of 100 adolescent girls was recruited for the study. A self-administrated questionnaire and Menstruation Attitude Questionnaire (MAQ) were used for data collection. Results: The level of knowledge was more significantly higher among urban girls and those with a higher level of education. Two-thirds had a satisfactory level of knowledge; more than two-thirds used sanitary pads as the ideal use during menstruation. The participants agreed that menstruation is a debilitating among 42 girls (42%), a bothersome among 15 girls (15%) and natural event among 53 girls (53%). Furthermore, they agreed that they can anticipate their menstruation among 80 girls (80%) and they denied the effect of it among 8 girls (8%). The majority of participants were informed about menstruation from their mothers as the first source of information. There was a positive correlation between participants' score of knowledge and their attitude toward menstruation. Conclusions and Recommendations: adolescent girls had a satisfactory level of knowledge about menstruation. Their mothers were the main source of information. The level of knowledge positively correlated with the girls attitude toward menstruation It is recommended to prepare girls for menstruation before menarche through providing them with well-planned school health program for girls and mothers about menstruation by well-trained educators.