.....End-stage renal disease (ESRD) patients have a severely immunologically aged T-cell compartment but also a high prevalence of CMV infection. We investigated whether CMV-infection contributes to T-cell ageing in ESRD patients. We determined the thymic output by the T-cell receptor excision circle (TREC) content and percentage of CD31+ naïve T cells. The proliferative history of the T-cell compartment by determination of the relative telomere length (RTL) and the T-cell differentiation status was determined by immunophenotyping. It appeared that CMV infection did not affect thymic output but reduced RTL of CD8+ T cells in ESRD patients. Moreover, increased T-cell differentiation was observed with higher percentages of CD57+ and CD28null CD4+ and CD8+ memory T cells. These CD28null T cells had significantly shorter telomeres compared to CD28+ T cells. Therefore we concluded that CMV infection does not affect the decreased thymic output but increases T-cell differentiation as observed in ESRD-related premature T-cell ageing.