Phagocytosis is central to immunity however a rapid and standardized method is much needed for quantitative assessment of the phagocytic process. We developed a real-time flow cytometric method to quantitate the phagocytosis of fluorescent latex beads by human monocytes in serum-free conditions. Human peripheral blood mononuclear cells were labeled with FITC conjugated CD16 and APC conjugated CD14, the uptake of 1 µm carboxylated Yellow-Orange (YO) beads was recorded in real time by flow cytometry on gated CD16+CD14+ monocytes. The innate phagocytic ability of human monocytes from single subjects measured by this method was relatively stable over many months although phagocytosis rate varied as much as two-fold between individuals. This method also allows tri-colour flow cytometric measurement of cytosolic calcium levels during the phagocytic uptake of fluorescent beads. By using this method, we have found that innate phagocytosis is completely abolished in the presence of serum, probably due to certain copper-binding glycoproteins, while Copaxone, a drug currently used in clinic to treat multiple sclerosis patients, dramatically promotes the phagocytosis ability of CD16-CD14+ monocyte.