Healing wounds in the oral mucosa of rhesus monkeys were examined by an immunofluorescence staining method to demonstrate the distribution of a blood group antigen cross reacting with human group B, and by labelling with tritiated thymidine to localize areas of cell proliferation. Within hours, blood group antigen reactivity was lost from epithelial cells adjacent to the wound margin. Reactivity was absent from the epithelial outgrowth into the wound, but returned with restoration of epithelial continuity. The zone of increased cell proliferation lay adjacent to, but outside of, the area of antigen loss. Antigen loss appeared to be associated with an area of increased cell movement, a finding of interest in relation to reports of antigen loss from epithelial tumors.