Premenstrual syndrome is a common but distressing entity among young females. It has attracted the attention of several studies which sought to evaluate the prevalence in several locations. In Jos, particularly among the undergraduate students of the university of Jos, we have not fully assessed the severity of this syndrome. This study was undertaken to assess the determinants of the severity of premenstrual syndrome in Jos among the undergraduate students. 449 students who gave their informed consent were recruited into the study, using pre determined questionnaire and the ICD 10 criteria for the screening of the syndrome. PMSA was diagnosed among 94.7% of the participants. Severity manifested in social withdrawal and breast tenderness (69.3% and 77.1% respectively). The limitation of activities was not a common report. It is concluded that the premenstrual syndrome is common among the undergraduate students of the University of Jos, with social withdrawal and breast tenderness as the manifestations of is severity.