In a prospective study, nine patients with osteoid osteoma were treated with a selective cyclooxygenase-2 inhibitor (rofecoxib). Patient pain perception with no treatment, with conventional nonsteroidal anti-inflammatory drug (NSAID) treatment, and with rofecoxib therapy was compared using a visual analog scale. Tumor response was also monitored by radiographs, computed tomography, and bone scintigraphy. In all cases, pain diminished on administration of rofecoxiib in comparison to conventional NSAIDs (P < .05). Four patients underwent surgery whereas in the remaining five patients, bone scintigraphy showed reduced uptake after 6 months. In four patients who were retested at 12 months,scintigraphy values were normal. These four patients are currently asymptomatic and are not receiving any treatment, whereas the fifth patient is still receiving therapy.