The authors made an electron-microscopic observation of intraepidermic vesiculation in pemphigus vulgaris at its early stage, and found that numerous macrophages were invading the cleft located immediately superior to the basal cell layer. They suggest that the formation of cleft, as a preceding stage to the eventual development into intraepidermic vesiculation, is intimately related to the squeezing-in of invasive macrophages among keratinocytes.