Repository therapy with an emulsified antigen preparation for pollen asthma and hay fever was used over the past three years. Overall results indicate that the response in the majority of patients was as good as that obtained with conventional preseasonal or perennial treatment. Reactions were noted in four of the 15 patients so treated during the first year of study, in 25 of 58 patients treated in the second year, and in 11 of 175 treated in the final year. These varied from mild to severe systemic reactions, some of which required hospitalization. With improvement and modification of the technique, such as the administration of the antigen in two injections rather than in a single injection, the incidence and severity of reactions were markedly reduced. The procedure is not without hazard; it requires great care, and initial experience is best obtained in a hospital environment.