The Pig Health Control Association has run a monitoring scheme for atrophic rhinitis for 10 years. One criterion for qualification has been that the average six-monthly snout score should not exceed 0.5 (later 0.65). Eighteen qualifying herds have exceeded this limit on 56 occasions, with their average scores rising to 2.24; they were the subject of special investigations for relisting. No clinical, epidemiological or bacteriological evidence could be found to indicate that these herds were capable of developing severe atrophic rhinitis. The higher snout scores were associated with a group of recurrent husbandry factors, especially overstocking and unsatisfactory conditions in the weaner accommodation. It is possible that the upper limit for the snout score in qualifying herds could be raised considerably, thus confining bacteriological testing to more doubtful herds.