**Abstract**

Uropathogenic *Escherichia coli* (UPEC) strains are those that cause infections in the urinary tract. They acquired virulence factors which enable them to survive in the urinary tract and elicit pathogenicity. The virulence factors are classified into two categories: (i) bacterial cell surface virulence factors and (ii) bacteria secreted virulence factors. Adhesins, toxins and iron up-take systems are major groups of virulence factors. The variety of virulence factors of UPEC is presented in this chapter.

**Keywords:** extraintestinal *E. coli*, uropathogenic *Escherichia coli*, urinary tract infection
