For quantification of histochemical reactions, color image analysis, as well as cytophotometry, is important. However, the extremely large amount of information, usually more than one million bits per image, involved in one microscopic picture of a colored histochemical specimen, when digitalized, has inhibited attempts to develop a more convenient system of color image analysis. Recent advances in microcomputer technology have now made it possible to build, at a reasonable cost, an intelligent color terminal equipped with array-processing hardware, a sufficiently large video random-access memory to represent 4096 colors in each pixel, and packages of machine language subroutines called "macro-commands" in the form of read-only memory that can process color images within a few seconds. This intelligent terminal can easily be controlled by a small personal computer via an IEEE-488 interface bus. The digitalized color image can be stored in and retrieved from a floppy disk. As the macro-commands in this system are controlled by BASIC program through CALLS with parameters, it is highly flexible and adapts readily to the varied needs of histochemists. Reported on herein will be the instrumentation of the microcomputer-based color image analyzer and a few examples of applications of this system to histochemistry: color intensification of cytochemical reactions, quantification of enzyme (e.g., horseradish peroxidase) reaction products, periodicacid-Schiff staining, collagen fibers visualized by Azan-Mallory stain, etc. Possible future applications of this color image analyzer will also be discussed.