Urticaria pigmentosa (mastocystosis) is a systemic disease characterized by tissue mast-cell hyperplasia in the corium of the skin and in the host organs of the reticuloendothelial system. One of the most frequently involved of these host organs is the skeletal system of the body. A survey of the literature reveals thirty-six cases of apparent urticaria pigmentosa with bone involvement but without histological confirmation. Twenty-one cases of urticaria pigmentosa with histologically proved bone involvement were found and summarized and an additional case is reported.