In patients with herpes virus dendritic epithelial keratitis, the pathologic morphogenesis of the dendritic lesion was investigated by means of impression cytology. Impression specimens were taken from the lesions of 24 consecutive patients assessed with a slit lamp biomicroscope. After a Millipore membrane impression was stained with hematoxylin-eosin and examined by light microscope, cellular patterns were analyzed. The results of these examinations showed that most cells were epithelial cells; there were also occasional multinucleated syncytial giant cells, inclusion bodies and inflammatory cells. Basal epithelial cells were most prominent at the actively infected lesion, whereas superficial epithelial cells were shown at the margin of the active lesion and terminal bulb. These findings suggest that in dendritic keratitis, viral spread and replication in the dendritic keratitis may progress through basal epithelial cells along the nerve within the basal epithelium-stromal interface.