Summary Five patients with extrinsic allergic alveolitis, due to Bird Fancier’s Disease are described. Four acquired their disease from pigeons and one from budgerigars. Four patients made a good recovery but one, a girl of 14 years who had the most severe disease initially, did not improve and progressed to pulmonary fibrosis and cor pulmonale. The clinical, radiological, pathological, immunological and pulmonary function details are discussed and the literature reviewed.