Infectious diseases remain a major cause of morbidity and mortality in CRF. Infection is the second leading cause of death in HD patients after cardiovascular disease. In the present work, monocyte CD14 expression and CD14/CD16 coexpression were studied in CRF and HD patients in a trial to clarify their impact on monocyte phagocytic activity. CD14 expression revealed significant reduction in CRF and HD patients before the session in comparison to controls however, at the end of the session it was significantly increased reaching nearly normal values. CD14/CD16 coexpression was significantly increased in CRF and HD patients when compared to the controls. The HD session resulted in significant increase in the coexpression in comparison to that before the session. Monocyte phagocytic % and index were significantly decreased in CRF and HD patients versus healthy controls. In addition, at the end of the session these parameters were significantly decreased compared to their values before the session. There was a significant inverse correlation between monocyte CD14/CD16 coexpression and phagocytic % in CRF and HD patients before and at the end of the session. This correlation could be explained by the fact that CD14+ CD16+ monocytes represent a more mature activated and senescent subpopulation of monocytes with decreased phagocytic activity. It could be concluded that CRF and HD patients had a significant increase in monocyte CD14 CD16 coexpression correlated with significant reduction in monocyte phagocytic activity. HD session with cuprophane membrane led to significant expansion in CD14+ CD16+ monocytes which amplified the defective monocyte phagocytosis.