The prevalence rate of allergic rhinitis and the consultation rate caused by this disease were studied in 131 general practices covering a population of 450,000 persons in Denmark. During a 1-year period starting June 1977 all consultations with or without symptoms were recorded. Allergic rhinitis was defined as paroxysmal sneezing and rhinorrhoea with or without conjunctivitis, and without signs of infection. Results are presented from three groups of practices classified by self-estimated completeness of reporting. 11--15 per thousand of the total population contacted a practice during the 1-year period (males: 12--17%, females: 10--13%). The highest prevalence rate occurred at 10--19 years of age, and allergic rhinitis was common from five to 44 years of age. The prevalence rate was higher among males up to the age of 30, after which age it was a little higher among females. About two-thirds of the patients consulting had at least one consultation per year with symptoms present. The number of contacts came to 4.4 per patient per year and 20--25% of these were with symptoms.