The fibroblastic tumor is among the most common of all the soft tissue tumors involving the extremities and is exceeded in number only by the benign lipoma. The tumor may originate from any area in the connective tissue stroma of the limb and therefore may be found attached to, or growing within, any of its special structures. Fibroblastic tumors range in degree of malignancy from the questionably neoplastic fibrous nodule, which arises as a reparative reaction to local irritation, to the malignant fibrosarcoma. However, such tumors, regardless of form or area of origin, present a clinical and pathologic similarity which justifies their inclusion in a single group. It is partly the object of this paper to demonstrate this fact and to demarcate the group of tumors to which it applies. Before entering into a discussion of their special characteristics, it is necessary that a clear definition of terms be given.