Menstruation is a normal physiological process that is managed differently according to various social and cultural understandings. Therefore, this cross-sectional study was conducted to explore the menstrual practices among 1275 female adolescents of urban Karachi, Pakistan from April to October 2006 by using interviews. Data was entered and analyzed in Epi Info Version 9 and SPSS Version 10. Descriptive findings showed that 50% of the girls lacked an understanding of the origin of menstrual blood and those with a prior knowledge of menarche had gained it primarily through conversations with their mothers. Many reported having fear at the first experience of bleeding. Nearly 50% of the participants reported that they did not take baths during menstruation. In univariate analysis, factors of using unhygienic material, using washcloths, and not drying under sun were found to be significant in the Chi square test among those going and not going to schools. This study concludes that there are unhygienic practices and misconceptions among girls requiring action by health care professionals. (Contains 3 tables.)