In summary, the epidemiological data and characterization of allergic and nonallergic rhinitis has been reviewed. Chronic rhinitis symptoms are among the most common problems presenting to physicians. When approaching this problem the diagnostic challenge is to determine the etiology, specifically whether it is allergic, nonallergic, or perhaps an overlap of both conditions. Estimates of the prevalence of allergic rhinitis range from as low as 9% to as high as 42%. Although the prevalence of nonallergic rhinitis has not been studied definitively, it appears to be very common with an estimated prevalence in the United States of approximately 19 million. In comparison, the prevalence of mixed rhinitis is approximately 26 million, and allergic rhinitis ("pure" and "mixed" combined) 58 million. Challenges in the differential diagnosis of rhinitis result from two major factors. Not only are presenting symptoms of allergic, nonallergic, and mixed rhinitis often indistinguishable from one another, but also the differential diagnosis of nonallergic rhinitis is extensive. Nonallergic rhinitis is often characterized by onset after age 20, female predominance, nasal hyperactivity, perennial symptoms, and nasal eosinophilia in approximately one-third of the population. Positive tests for relevant specific IgE sensitivity in the setting of rhinitis do not rule out "mixed rhinitis" and may not rule out nonallergic rhinitis. The significance of symptom exacerbation by nonallergic triggers in the setting of allergic rhinitis remains to be determined. Goals for the future include reaching a consensus on the definitions of rhinitis and rhinitis subtypes including the establishment of mixed rhinitis, updating guidelines for the interpretation of nonrelevant positive tests for specific IgE sensitivity, and reaching agreement on the nonallergic triggers that best define VMR or VMR subtypes. Only then can the most applicable research results be obtained. The desired result is the delivery of the most appropriate treatment, specifically tailored to the accurate diagnosis of patients with rhinitis.