Urotensin II (UII) is a potent peptide hormone with a complex species and vessel-dependent vascular profile. UII and the homologous UII-related peptide (URP) bind to the g-protein coupled urotensin II receptor (UT) with high affinity. The peptide ligands and receptor have been detected in numerous human and rat tissues including heart, brain and kidney. The kidney is a major source of UII, which appears to act as both an endocrine and paracrine mediator of renal function. UII has been shown to influence renal blood flow, glomerular filtration rate and sodium handling in the renal tubules. More speculative actions of UII as a pro-fibrotic mediator include the activation of fibroblasts and promotion of collagen synthesis. Abnormally elevated UII, URP and UT expression has been highlighted in a number of cardio-renal disease states; particularly end stage renal disease, diabetes and diabetic nephropathy (DN). This work aims to investigate the role of the UII system in the development and progression of CKD using an experimental model of CKD in rodents. The first aim of the current work involved establishing the surgical 5/6th subtotal nephrectomy (SNx) model of chronic kidney disease (CKD) in the laboratory and forming a profile of UII expression in late stage experimental CKD to complement UII clinical data which are exclusively from patients in the later stages of disease. UII/URP and UT were substantially over-expressed in the kidneys of SNx rats in late stage CKD. This novel insight complements the clinical profile of CKD/DN where over expression of the UII system is routinely reported.In a second study the 5/6th SNx rat model was used to explore the effects of chronic UT receptor antagonism on the progression of CKD. Although there were no discernible differences in kidney mass or histological profile between the treatment groups at the end of the study, there was a small delay in the development of albuminuria and in the onset of systolic blood pressure elevation in the UT antagonist treated cohort. The study did not produce clear-cut evidence defining the potential therapeutic value of UT-antagonism in the treatment of CKD. Despite this the results are encouraging and suggest that the role of UT-inhibition in CKD is worth considering further.