Computer-based assessment of images acquired in a microscope requires an attached video camera transferring the images to a computer and a screen. The analytical decisions made by the computer equipped with a special software program will be displayed on the screen in discriminating pseudocolors, enabling the operator to monitor and accept or discard the results of a given field. Quantification of cells expressing cell surface antigens or intracellular antigens can be readily done in immunohistochemically stained tissue sections from synovial tissue. Conventional microscopy is a good tool for counting but poor at measuring areas, staining intensity, or distances, which can be handled in a superior way by computer-assisted analysis. We have successfully applied this technology to quantify the incidence of various cell types, intimal layer thickness, and cytokine-producing cells in rheumatoid synovial tissue specimens. Computerized image analysis offers a major advantage in sequential studies to evaluate changes in response to therapy.