Background: Menstrual cycle abnormalities have been considered a common occurrence during puberty. Numerous earlier studies have analyzed the various patterns seen in the epidemiological data regarding menstrual cycle of adolescent girls. But there is dearth of data from Rohilkhand region of central UP state. Aims: To find out the abnormal menstrual patterns among adolescent girls in Bareilly city. Materials and Methods: A cross sectional study conducted by presenting a pre-designed and pre-tested self administered questionnaire, containing questions pertaining to menstrual practices and knowledge to 994 adolescent girls of urban schools in Bareilly city. Results: Mean age of menarche was 13.11±0.95 years. 6.07% girls in the study reported cycles of abnormal lengths. This subset also had significantly higher prevalence of irregularity. Presence of irregular menses beyond 3 gynaecological years diminished the possibility of their regularization in near future. Among the girls with excessive dysmenorrhea, nearly 1/3rd had associated menstrual disturbances also. Conclusion: Incidence of irregular menstrual cycle was 20.75% and it was significantly more in oligomennorheic cycles. Among normal menstrual cycles also, presence of IMC was significantly more in adolescents having mild oligomennorhea. 6.07% of girls reported abnormal cycle lengths. 77.70% reported dysmennorhea. Chances of menstrual cycles getting regularized after 5 years of menarchy are minimal. Adequate knowledge regarding abnormal variations in the menstrual cycle pattern during adolescence may permit implementation of strategies for preventing potential reproductive and other health morbidities in adulthood.