Adolescence is a significant period characterized by growth, developmental, needs and rights. Dysmenorrhea is a severe, painful, cramping sensation in the lower abdomen and has different detrimental effects on females and the community. The study aimed to determine the prevalence of dysmenorrhea among secondary girl Students. Subject and Methods: Descriptive cross sectional research design was used in this study. It was conducted in four secondary girl schools at Assiut city by using multi stage random sample of 666 students who participated in the study, while the girl students having dysmenorrhea represent 515.Three tools were used for data collection, first tools: A structured self-administered questionnaire which consisted of two parts: part I: included personal characteristics, part II: knowledge about menstruation and dysmenorrhea .Second tools: Verbal Multidimensional Scoring System (VMS). Third tools: Visual Analogue scale used to assess the severity of dysmenorrhea. Results: The mean age of studied students ± SD was 16.31 ± 0.91(15.0-19.0), more than two thirds (77.3%) of them suffering from dysmenorrhea. Conclusion: More than three quarters of secondary girl students suffering from dysmenorrhea Recommendation: Increase awareness of students regarding menstruation and dysmenorrhea through mass media. Health education program to students, teacher and school health nurses about menstruation, dysmenorrhea and how to relive pain.