Several surface receptors are expressed on eosinophils in vitro depending on the state of cellular activation, but immunohistochemical studies of eosinophil-related diseases have mostly focused on the number of infiltrating eosinophils as well as extracellular deposits of eosinophil granule proteins. The present investigation showed that eosinophils display a characteristic granular appearance in cryo-sections and cytospins by differential interference contrast (DIC) imaging. This approach appeared to be more reliable for identification of these cells in situ than immunohistochemical labelling of eosinophil granule proteins. Moreover, combined with immunofluorescence microscopy DIC imaging facilitated three-colour immunofluorescence phenotyping of eosinophils.