This is a three year grant studying the role of hydroxyurea in the treatment of primary and recurrent Desmoid Tumors in adults and children. Hydroxyurea is a generally well tolerated anti-neoplastic agent used in the treatment of myeloproliferative disease, CML and small group of carcinomas. This study builds on the favorable efficacy:toxicity experience in an earlier study in children in which preliminary results showed partial response or stable disease in 79% of patients. This is a non-randomized trial.