AbstractThis study was directed toward a comparison of the effectiveness of three different light‐microscopical methods for identifying and studying the features of cells that contain horseradish peroxidase (HRP) granules. The cells studied were located in the trigeminal ganglia and were labeled after the injection of HRP solutions into single, maxillary, canine teeth. The tissue was examined with light field, dark field, and differential interference optics systems. The results indicated that differential interference optics were especially useful in revealing the presence of intracellular HRP granules in both unstained and stained tissue, particularly when cells only contained small amounts of HRP. It was also noted that a wide variety of quantitative analyses could be performed with differential interference optics, even when using unstained tissu