The effect of different intraperitoneal dwell times on the phagocytic capacity of the effluent-derived macrophages in 6 peritoneal dialysis patients was studied. The number of peritoneal cells increased after longer dwell times, and a significant increase in the percentage of macrophages phagocytosing opsonized sheep red blood cells ([IgG]SRBC) and unopsonized latex beads was determined when the dwell time increased from 1.5 to 15 h. Thus, the total phagocytic capacity of the effluent-derived macrophages dramatically increased with prolonged dwell times. In addition, the IgG concentration showed a five-fold increase following long intraperitoneal dwell times. The increasing IgG levels were accompanied by an increase, however not significant (p