To compare the efficacy of bulb and catheter suctioning of upper airway meconium in neonates, meconium labeled with technetium Tc 99m sulfur colloid was injected into the trachea and oropharynx of anesthetized kittens. Human birth conditions were simulated by an inflated blood pressure cuff around the thorax and abdomen of the animals and by partial degassing of the lungs before introduction of meconium. Distribution of meconium in the upper airway was determined by scintigraph. Catheter suction brought about a 43% decrease in radioactivity, while there was only a 1% decrease after bulb suctioning. Meconium may persist in the trachea for more than 20 minutes after introduction, indicating the desirability of continued suctioning efforts in neonates with meconium aspiration syndrome. The relative safety of the two techniques was not assessed.