Cryosurgery and acrylic cementation as surgical adjuncts in the treatment of aggressive (benign) bone tumors. Analysis of 25 patients below the age of 21. This article reviews the clinical experience with cryosurgery (use of liquid nitrogen) and acrylic cementation (polymethylmethacrylate; PMMA) in the treatment of aggressive, benign bone sarcomas and the biologic basis of this technique. The results of 25 patients below the age of 21 treated by cryosurgery, with an average follow-up period of 60.8 months, are reported. Three approaches to surgical reconstruction were used: Group 1 (four patients) had cryosurgery with no reconstruction, Group 2 (13 patients) had bone graft reconstruction alone, and Group 3 (eight patients) had composite osteosynthesis with internal fixation, bone graft, and/or PMMA. The overall control rate was 96% (one recurrence). The tumor types were giant-cell tumor, chondroblastoma, aneurysmal bone cyst, and malignant giant-cell tumor. Nineteen lesions involved the lower extremity, and six lesions were located in the upper extremity. There were two secondary fractures (8%), one local flap necrosis, and one synovial fistula. There were no infections. Two epiphyseodeses were performed. The functional results were excellent (83%), good (13%), and fair (4%). The technique of composite osteosynthesis is recommended for all large tumors of the lower extremity. Cryosurgical results compare favorably with those obtained by en bloc resection and demonstrate the ability of cryosurgery to eradicate tumors while avoiding the need for extensive resections and reconstructive procedures. 