Three cases of severe bronchospasm occurring in known asthmatics following the administration of enflurance are described. Other commonly known causes of bronchospasm did not seem to be operative. Moderately high concentrations of halothane in the respired gases protected against the bronchospasm whereas a moderately high blood concentration did not. Although the authors have administered enflurane to other known asthmatics without producing bronchospasm, they feel it should be used with caution in such patients.