After one hour cross-linked agarose encapsulated activated charcoal hemoperfusion, there was slight increase of total white cells and neutrophil count, but the neutrophil adherence was 16.87 +/- 5.26% and marked lower than that before hemoperfusion (59.91 +/- 5.26%, p less than 0.05). Using glassball hemoperfusion as control, the neutrophil adherence also decreased but not so obvious as the former. Adherence is a cell property that may affect granulocyte margination, diapedesis, chemotaxis and phagocytic function, so the above investigations showed that both the hemoperfusion process and the charcoal itself may reduce the host defence mechanism. There were no change of the peroxidase and alkaline phosphatase activities of neutrophils during one hour cross-linked agarose encapsulated activated charcoal hemoperfusion.