The presence of mast cells, often in an activated state or increased numbers, has been noted in various cutaneous disorders. Recent studies suggest that mast cells are of primary importance in these conditions and their presence does not merely represent a secondary event. This review focuses on atopic dermatitis, contact hypersensitivity reactions, bullous pemphigoid, fibrosing conditions, neurofibromatosis, wound healing, polycythemia vera, and psoriasis, in which there is significant evidence to indicate a pathophysiologic role for mast cells.