The effect of positioning on pulmonary function has been previously evaluated, and the prone position has been reported to be preferable for neonates with various respiratory diseases. Studies in healthy neonates have yielded conflicting results. Using a crying pulmonary function test, we examined the effect of positioning on pulmonary function in healthy full‐term neonates. Thirty‐nine infants with a mean birthweight (± SD) of 3,140 ± 379 g and a mean gestational age (± SD) of 39.8 ± 1.6 weeks were investigated during the first 6 hours of life. Measurements were obtained in both supine and prone positions using a computerized volume‐flow system. There were statistically significant decreases in crying vital capacity (CVC) and peak expiratory flow rate (PEF) in the prone compared with the supine position. However, there were no significant differences in forced expiratory flow rate at 75% (V75), 50% (V50), and 25% (V25) of vital capacity between the two positions. These results suggest that prone positioning decreases lung volume and increases resistance of upper airways. We conclude that healthy neonates should be in the supine posture for optimal ventilation. Pediatr Pulmonol. 1996; 21:167–170. © 1996 Wiley‐Liss, Inc.