Objective: The aim of this study was to document sensory changes in the supraorbital, infraorbital, and mental nerve distributions following acute and chronic maxillary and frontal sinusitis. Method and Materials: Seven patients with a total of 14 infected sinuses were included in the study. Neurosensory function was evaluated by measuring the electrical detection threshold for large myelinated nerve fibers and heat detection thresholds for the assessment of the thin unmyelinated nerve fibers. The sensory tests were conducted in the infraorbital, supraorbital, and mental dermatomes. Patient evaluation included clinical examination and computerized tomographic imaging of the sinuses. Sinusitis symptoms of 1 month or less were considered acute, and symptoms that persisted for more than 3 months were considered chronic. Detection thresholds in 8 healthy volunteers served as controls. Results: Eight acute and 6 chronic sinusitis cases were diagnosed. Acute sinusitis produced bilateral large myelinated fiber hypersensitiv-ity (electrical) relative to healthy controls, with no significant change in the thin unmyelinated nerve fiber detection threshold (thermal). Chronic sinusitis resulted in large myelinated fiber hyposensitivity and thin myelinated fiber bilateral hyposensitivity, as compared to healthy controls. Conclusions: This study concurs with previous studies in finding that early inflammatory neuritis can produce large myelinated nerve fiber hypersensitivity, while long-lasting processes, presumably accompanied with early nerve damage, may result in hyposensitivity. Keywords: neuritis, neuropathic pain, quantitative sensory testing, sinusitis