The olfactory mucosa was examined by immunohistochemistry in patients with olfactory disturbance: anosmia due to choanal atresia and chronic sinusitis, early-stage common cold, late-stage common cold, and head trauma. The results indicate that the olfactory mucosa of patients with olfactory disturbance shows specific kinds of immunoreactive patterns and that immunohistochemistry is useful for examining the degree of degeneration of pathologic human olfactory mucosa and for clarification of prognosis.