The high incidence of cardiovascular complications in patients with chronic renal failure (CRF) is partly explained by more aggressive atherosclerosis, i.e. increased incidence and severity of lesions with higher tendency to calcification. The pathogenesis of this accelerated atherosclerosis, however, is not completely understood. Among other risk factors, chronic micro-inflammation may be involved. Activation of cells and adhesion molecules in atherosclerosis is governed by CD40-CD154 (CD40 ligand) interaction. Therefore, we investigated the expression and distribution of CD40-CD154 in different coronary atherosclerotic lesions of CRF patients and non-renal control patients. Coronary plaques of 57 patients with and without CRF were categorized according to the Stary classification and analysed for in situ protein expression of CD40, CD154 and CRP using immunohistochemistry and a semiquantitative scoring system. The nature, number and distribution of infiltrating cells was analysed and correlated to the types of coronary lesions and in particular to the presence of calcification. CD40 was over expressed in media myocytes of coronary plaques of both uremic and control patients. Inside the plaques, CD40 was expressed on endothelial cells, T lymphocytes, macrophages, fibroblasts, and smooth muscle cells. CD154 expression was seen on T cells in areas densely infiltrated by CD40 positive macrophages. In uremic and control patients higher in situ expression of CD40, CD154 and CRP was seen in calcified compared to non-calcified lesions. Inside the plaques, there were significant differences in the expression pattern of CD40 and CD154 between uremic and control patients. In addition, in uremic patients coronary plaques showed higher CRP protein expression compared to control patients. The data indicate a higher inflammatory status of coronary lesions as well as involvement of the CD40-CD154 signaling cascade in CRF patients, especially in cases of calcified atherosclerotic lesions.