Thirty-one patients with osteoid-osteoma and eleven patients with osteoblastoma of the spine were evaluated after operative excision of the tumor. The average duration of symptoms in the seventeen patients whose tumor had been diagnosed by technetium bone-scanning was twelve months, as compared with thirty-five months in the twenty-five patients who had been diagnosed without the aid of bone-scanning. There were no false-negative bone scans. Scoliosis was present in fourteen of eighteen patients with a lumbar lesion, in ten patients with a thoracic lesion, and in two of the twelve patients with a cervical lesion. Twelve of the twenty-six patients with scoliosis had had symptoms for less than fifteen months before diagnosis (Group A), and eleven had had symptoms for more than fifteen months (Group B). The duration of symptoms was unknown in the other three patients. Eleven of the twelve patients in Group A had a decrease in or complete correction of scoliosis after excision of the tumor, whereas ten of the eleven patients in Group B had no decrease in the pre-operative scoliosis.