Uropathogenic E. coli have special features that allow them to take advantage of the bladder environment. There UPEC can grow to substantial numbers in pure culture that are shed frequently into the environment and have a high probability of transmission to other hosts. A better understanding of the transmission system and the host and bacterial factors influencing transmission is essential for the identification of effective prevention strategies. Although the risk of severe morbidity among otherwise healthy populations is low, the incidence is high. Further, the potential impact of antibiotic treatment on the emergence of increasingly antibiotic-resistant UPEC (the resistant mechanisms that may be transmitted to other bowel inhabitants) is high. The benefits of successfully preventing UTI are substantial.