Mucosal changes have been well described in chronic sinusitis, yet little is known about the underlying bone, despite clinical and experimental evidence suggesting that bone may be involved in chronic sinusitis. Techniques of undecalcified bone analysis were used for detailed histologic examination of ethmoid bone in chronic sinusitis compared with controls. Bone synthesis, resorption, and inflammatory cell presence were specifically assessed. Additionally, histomorphometry techniques were used to determine ethmoid bone physiology in individuals undergoing surgery for chronic sinusitis. Overall, individuals undergoing surgery for chronic sinusitis were found to have evidence of marked acceleration in bone physiology with histologic changes including new bone formation, fibrosis, and presence of inflammatory cells. These findings are compared with osteomyelitis in long bone and the jaw. The suggestion that underlying bone may serve as a catalyst for chronic sinusitis is supported and implications for therapy are discussed.