Dendritic Langerhans cells (LCs) were identified in flat-mount preparations of mouse corneal epithelium after staining for ATPase activity. They were found predominantly in the limbus, but after inoculating the cornea with HSV1 strain SC16 LC, numbers increased both in the limbus and the central cornea. Numbers of LCs reached a maximum on day 8 and if severe keratitis was present remained high at least until day 22. A small but significant increase in LCs was also found in the opposite, uninoculated eye in mice with severe damage in the inoculated eye. After HSV inoculation on the snout, 60% of mice had corneal disease in the eye on the inoculated side; in such mice corneal LCs were at a maximum 18 days after inoculation. The increase in LC numbers was similar whether inoculation was into the cornea or in the snout. After corneal inoculation the cells were distributed fairly evenly over the corneal surface, with accumulations limited to epithelial ulcers. However, after inoculation on the snout, numerous clusters were seen over the epithelial surface, often surround by epithelium devoid of LCs.