OBJECTIVES: Osteomas are common benign tumors of the paranasal sinuses. The origin of these lesions is uncertain. Although most are asymptomatic, symptoms can include headaches, facial pain, rhinorrhea, and sinusitis. Osteomas are also seen as part of Gardner's syndrome, an autosomal dominant disease characterized by intestinal polyposis, osteomas, and cutaneous and soft tissue tumors. In affected individuals, the risk of developing colon cancer approaches 100%. On average, osteomas are detected 17 years before colon polyps appear. METHODS: Three patients with maxillary or ethmoid osteomas and chronic sinusitis are presented. RESULTS: One of the patients had evidence of Gardner's syndrome, based on the presence of gastrointestinal symptoms and a positive family history of polyposis. CONCLUSIONS: Otolaryngologists should be aware of the possibility of Gardner's syndrome in patients with paranasal sinus osteomas. Suspected patients should have a complete workup for Gardner's syndrome, including lower gastrointestinal tract endoscopy, barium enema imaging, and DNA testing.