ABSTRACT Background : Dismenorrhea is the most common gynecological complaint experienced by adolescents and women who are in their early adulthood. Dismenorrhea can affect a woman's quality of life during reproductive times, such as loss of employment opportunities, disrupting learning activities in school and disrupting family life. One of the causes often associated with dismenorrhea is the Body Mass Index (BMI). Abnormal BMI can cause pain in menstruation or dysmenorrhea. Knowing the relationship of Body Mass Index (BMI) with the degree of dismenorrhea in medical students FKIK University of Jambi.Method : This research uses cross sectional design. The population in this study was medical student of FKIK University of Jambi class of 2018 and 2019. The number of samples in this study was 104 and taken random sampling, by distributing questionnaires in the form of google form to respondents.Result : The results showed that there is a relationship of Body Mass Index (BMI) with the degree of dismenorrhea obtained p-value = 0.000. Obtained underweight BMI data and suffered a mild dismenorrhea - while as many as 19 people (24.67%), who experienced severe dismenorrhea as many as 2 people (7.41%). For overweight BMI and mild dismenorrhea - moderate as many as 9 people (11.69%), who experienced severe dismenorrhea as many as 17 people (62.96%). For normal BMI and mild dismenorrhea - moderate as many as 49 people (63.64%), who experienced severe dismenorrhea as many as 8 people (29.63%).Conclusion: There is a relationship between Body Mass Index (BMI) and degree of dismenorrhea.