In a series of fibrotic and sclerotic diseases including scars, keloids, fibromas, scleroderma and lichen sclerosus et atrophicus, we found modifications in the dendrocyte population. Dendrocytes were numerous in fibrotic diseases associated with little deposits of collagen. Conversely, they were almost absent in sclerotic diseases when the lay-down of collagen was prominent. We hypothesize that dendrocytes, by their content in factor XIIIa, may limit the accumulation of collagen in the skin.