Abstract In their work upon human sensitization, in 1916, Cooke and Vander Veer (1) included a study of inheritance in a group of 504 cases of atopy2 This group comprised cases of hay fever, bronchial asthma, urticaria, angioneurotic edema and acute gastroenteritis following the ingestion of fish and strawberries. These authors stated that their study indicated a definite hereditary factor in hypersensitiveness as shown particularly by the influence of heredity on the age of onset of clinical symptoms. The present study was undertaken to determine whether or not their results would be verified on an entirely new series. Five hundred sixty-eight cases of hay fever and asthma are now presented, in all of which the hypersensitive condition was demonstrated by a positive intradermal test which was in complete accord with the clinical history.