We report a case of pigeon breeder’s lung in which chronic airflow obstruction and not restrictive lung disease was predominant. The patient’s disease was severe enough to require hospitalizations twice to reverse respiratory failure. Helium-oxygen flow volume curves were consistent with a peripheral site of flow limitation, and immunoserological studies disclosed specific IgE as well as precipitating antibody responses to pigeon antigens. Immunological studies on 18 other patients with pigeon breeder’s lung demonstrated a prevalence rate of specific IgE antibodies of 78%, a frequency not previously recognized. Exposures to avian antigens must be considered in patients with obstructive lung disease of unknown eti