The epithelial barrier of the female urogenital tract is kept free from infection by several physiological and immunological mechanisms [1]. The pathophysiological events in infection are hypothesised to start with bowel commensals colonising the vagina then ascending the urethra before invading bladder epithelium. Synthesis of antimicrobial peptides known as defensins are a key element of epithelial protection [2]. These act as a first-line defence, causing bacterial cell death by membrane disruption and inactivation of intracellular targets [3]. Several defensins have been identified in urine & vaginal fluids but their relative importance and precise role(s) remain unclear. With institutional and ethical approval, 20 tissue biopsies (5 renal, 5 ureteric, 5 bladder & 5 vaginal) were taken from women during surgery. Reverse-transcriptase qPCR was used to identify relative expression of defensins and toll-like receptors. For highly expressed defensins, peptides were localised by immunohistochemistry. In vitro experiments using RT4 urothelial and VK2 vaginal cells were performed to assess defensin induction following challenge with Uropathogenic Escherichia coli (UPEC), 0.5 μg/ml lipopolysaccharide (LPS) and female hormones, oestrogen (1nM) and progesterone (2nM). Variable expression of defensins was seen according to anatomical site in the urogenital tract. In particular, both beta defensin 1 (BD1) and human defensin 5 (HD5) were highly expressed in the urinary tract, the former more so in the kidney, the latter in the ureter. Both BD1 and HD5 mRNA showed significant induction (>2 fold rise at 2 hrs, n=9, t-test p<0.05) in response to UPEC challenge of RT4 urothelial cells but only BD1 showed evidence of induction in response to LPS. VK2 vaginal cells responded differently with significantly increased basal levels of BD1 in response to oestrogen (>4 fold rise at 24 hrs, n=9, t-test p<0.05) and increased expression of beta defensin 2 (BD2) in response to LPS (>4 fold rise at 24 hrs, n=9, t-test p<0.05). These data suggest differing constitutive defensin expression along the urogenital tract which may reflect a graduated response to bacteria of varying virulence and mobility. Induction of BD1 and HD5 after UPEC challenge supports their role in defence against invasion but the differing response to LPS suggests each has a role at different stages within the sequence of infection. Furthermore, differences in the response of vaginal cells particularly under hormonal influence highlight the unique role of this epithelium in the defence against colonising pathogens. We speculate that differences in expression of epithelial defensins at these sites may play a role in recurrent urinary tract infection (rUTI) in susceptible women. We are collecting further in vivo data to investigate the relevance of these findings for women predisposed to rUTI.