Abstract: The present invention is embodied in a method and algorithm for rapidly quantifying phagocytic functions using computer image analysis (CIA) of video light microscopic images. The method and algorithm involve sequential acquisition of bright field or phase contrast and epi-fluorescence video microscopic images of respective field, addition of the images, decision making, object referencing, morphological feature extraction, arithmetic operations, and statistical analysis. This invention provides significantly faster phagocytic functions analysis than manual microscopic examination and more detailed quantitative morphological data than flow cytometery.