Rhinitis medicamentosa (RM) is a condition induced by overuse of nasal decongestants. The term RM, also called rebound or chemical rhinitis, is also used to describe the adverse nasal congestion that develops after using medications other than topical decongestants. Such medications include oral beta-adrenoceptor antagonists, antipsychotics, oral contraceptives, and antihypertensives. However, there are differences in the mechanism through which congestion is caused by topical nasal decongestants and oral medications. Very few prospective studies of RM have been performed and most of the knowledge about the condition comes from case reports and histologic studies. Histologic changes consistent with RM include nasociliary loss, squamous cell metaplasia, epithelial edema, epithelial cell denudation, goblet cell hyperplasia, increased expression of the epidermal growth factor receptor, and inflammatory cell infiltration. Since the cumulative dose of nasal decongestants or time period needed to initiate RM has not been conclusively determined, these medications should only be used for the shortest period necessary. Validated criteria need to be developed for better diagnosis of the condition. Stopping the nasal decongestant is the first-line treatment for RM. If necessary, intranasal glucocorticosteroids should be used to speed recovery.