Objective To assess the effects of gelatine and 6% hydroxyethyl starch 200/0.5 (HES 200 / 0.5) on phagocytic activity of human neutrophils and monocytes using flow cytometry.Methods Thirty-three ASA Ⅰ - Ⅱ patients aged 18-70 years scheduled for urological minor surgery were randomly divided into three equal groups of eleven patients :group I gelatine;group II HES 200 / 0.5 and group Ⅲ lactated Ringer's solution (LR) . 10 ml?kg-1 of gelatine, HES or LR was infused over 60 min and venous blood samples were taken before infusion and 1 h after the start of infusion for determination of phagocytes with ingested FITC-labeled E coli by flow cytometry. Results In gelatine group the percentage of neutrophils and monocytes with phagocytic activity decreased significantly after infusion ( P