OBJECTIVE: Few studies have compared the performance of nasal prongs used for applying continuous positive airway pressure. The present study compared the tolerance and efficacy with the Argyle and Hudson nasal prongs. DESIGN: A prospective, randomized clinical study. SETTING: A tertiary neonatal intensive care unit in a university hospital. PATIENTS: A total of 99 preterm infants weighing </=2500 g were assigned to one of three weight categories. They were then randomly assigned to use one of two nasal prong types. The number of times the prongs were out of the nostrils, time on nasal continuous positive airway pressure, respiratory and heart rate, Silverman-Andersen retraction score, blood gases, abdominal distention, nasal hyperemia and bleeding, septum necrosis, pneumothorax, and therapeutic success were documented. MEASUREMENTS AND MAIN RESULTS: The two groups were matched for weight, gestational age, and disease for which the continuous positive airway pressure was used. For patients weighing 1500-2000 g, the Hudson users had a greater gestational age. Both types of nasal prongs reduced the Silverman-Andersen retraction score in all infants 2 hrs after continuous positive airway pressure application, except for patients weighing </=1000 g. The Argyle prong was related to a higher frequency of hyperemia in babies weighing <1500 g (p =.03). There were no cases of septum necrosis or pneumothorax. The frequency of therapeutic success for patients using Hudson prongs and weighing >/=1500 g was significantly higher than for those using the Argyle catheter (p =.03). CONCLUSION: Considering the difference in gestational age for the patients weighing 1500-2500 g, we conclude that the two prongs tested are equally effective for nasal continuous positive airway pressure, but the Argyle prong is more difficult to keep in the nostrils of active patients, and nasal hyperemia, the first sign of tissue aggression, occurs more frequently among infants using this prong.