Among fifty-three Salt Lake City. Utah area pigeon fanciers, 21% were found to have the clinical picture of pigeon breeders disease. This is a much higher frequency than has been observed previously. Abnormal spirometry and increased skin reactivity to pigeon sera were found more often, statistically significantly, in symptomatic than in exposed asymptomatic fanciers. Pigeon breeders' disease is associated with a variety of abnormal findings; skin test, precipitins, pulmonary function changes and radio-graphic derangements: but unfortunately none of these are diagnostic. Pigeon breeders' disease is best identified by clinical criteria.