Sixteen stable intubated premature infants without a clinically significant patent ductus arteriosus were studied during recovery from respiratory distress syndrome in order to determine the effects of left and right lateral, as compared to supine, positioning. Pulmonary mechanics were measured for spontaneous breaths 5 and 15 minutes after positioning, and arterial blood gases 15 minutes after positioning. Infants were randomized to 1 of 2 position sequences: (1) supine, left, supine, right or (2) supine, right, supine, left. No significant differences were detected between positions for dynamic compliance, tidal volume/kg, and total, inspiratory and expiratory pulmonary resistance. Likewise, no significant differences in PaO2 or PaCO2 were detected between the positions. The sequence of positions did not affect the pulmonary mechanics of spontaneous breaths or arterial blood gases. This suggest that short-term lateral positioning as well as supine positioning can be utilized without deleterious effects on pulmonary mechanics and gas exchange in neonates recovering from respiratory distress syndrome.