Morphological changes in dermal collagen fibers in growing mink were investigated using a scanning electron microscope (SEM). The SEM view of dermal collagen fibers varied throughout the newborn, growing and mature skin phases. The reticular layer of newborn mink dermis was plate-like, and appears to be composed of fine collagen fibers, proteoglycans and glycoproteins. With mink growth, randomly entangled dermal collagen fibers, which were relatively fine and curled or waved, showed regularity of the three-dimensional network. A three-dimensional network of thick collagen fibers was observed in the mature mink dermis, and the fiber arrangement altered in relation to the depth from the epidermis, i. e., in the upper dermis, many fibers were arranged diagonally to the skin surface, whereas in the mid and deep dermis, thick fibers were conspicuously arranged parallel to the skin surface. The collagen fiber network was formed by repeated branching and anastomosis of the fibers. There were thin elastic fibers in the dermal-epidermal junction and between the collagen fibers and skin appendages.