Urinary tract infection (UTI) commonly occurs among young, otherwise healthy women in their sexually active years, and accounts for 3 percent of all physician visits in this group. Repeated UTIs are often difficult to treat and greatly disrupt a woman's life. The overall goal of the proposed study is to determine the individual and joint effects of bacterial and host characteristics and host behaviors on risk of recurring UTI among otherwise healthy young women with one prior UTI. Specifically, the investigators plan to conduct a prospective cohort study among 400 college-aged women who have had one prior UTI in order to: I.Characterize symptoms and severity of initial and subsequent UTIs among study participants and determine if these characteristics are associated with an increased risk of recurrence. II.Describe host behaviors prior and subsequent to the initial UT in those with and without recurrences and determine if these behaviors are associated with an increased risk of recurrence. III.Determine whether the bacteria causing recurrence belong to the same strain as those which caused the initial infection. IV.Identify each type of bacteria isolated from all the urine specimens of participants at initial UTI and assess whether bacterial characteristics of the initial infection strain(s) are associated with an increased risk of recurrence. V.Determine ABO, P, M, and Lewis blood type among participants, and assess whether blood phenotype predicts recurrence. VI.Determine if particular combinations of behaviors, blood type, and/or bacterial characteristics increase the risk of recurrence beyond the individual effects of these separate factors. At enrollment, participants will complete a self-administered questionnaire regarding medical history and behaviors in the recent past; their ABO, P, M, and Lewis blood types will be determined and the bacteria causing infection characterized. Women will be followed for the 6 months after their initial UTI via telephone interview and medical record review. The characteristics of bacteria causing repeated infection will be examined. Recurring UTI has a significant impact upon a woman's life. If the proposed study successfully identifies risk factors which, if modified, could prevent even a small proportion of recurring UTI, we will have made a significant contribution to women's health.