The effect of celery seed on isolated cat tracheal smooth muscle was determined in vitro. An alcoholic percolate was obtained from celery seed and the resulting liquid was concentrated and freeze dried. The median lethal dose concentration was determined and the resulting extract was tested for bronchodilating activitiy on isolated tracheal rings of cat using a tissue stabilization set up. Results show that the extract failed to antagonize acetylcholine-induced bronchoconstriction of the tracheal smooth muscle. The study also shows that the median lethal dose of celery seed extract is 2.1963 g/kg.