In 27 asthmatic patients a cell culture was made from mononuclear cell stimulated by PHA. Indomethacin was added to part of the cultures. After 2 days the culture was terminated and the supernatant was prepared for bronchoprovocation studies. Patients underwent baseline respiratory function studies, after which bronchial provocation was carried out with different concentrations of the supernatant. Bronchial provocation using supernatant from cells cultured with indomethacin produced significant respiratory function alterations in comparison with tests carried out with supernatant from cells stimulated with PHA.