To assess the usefulness of current diagnostic criteria in the understanding of neonatal respiratory distress in a tertiary care hospital.We prospectively studied 2824 consecutive deliveries to determine the frequency of respiratory disorders of all types. We used definitions based on standard texts, with borderline cases being classified as having the disease in question.Somewhat less than half of all symptomatic infants met textbook criteria for a respiratory diagnosis. Of this subset, the most common diagnosis was respiratory distress syndrome (RDS), followed by transient tachypnea of newborn (TTN), meconium aspiration syndrome (MAS), pneumonia and others. The 323 infants who fit no standard diagnosis all had self-limited conditions similar to TTN. Most (52%) were well in less than 12 hours. Those still symptomatic after 12 hours differed from the definition of TTN by having a clear chest film (38%) and/or by requiring mechanical ventilation (10%). A slight revision of the traditional diagnostic criteria allowed classification of all these cases.More than 50% of newborns with acute respiratory symptoms do not fit textbook definitions, even broad definitions which include borderline cases. The concept of TTN should be expanded to include cases with a normal chest film. In addition, we suggest adding the category "transient respiratory insufficiency of the newbom" (TRIN) for babies ventilated briefly but not demonstrably surfactant deficient or infected. This category probably includes infants with many contributing etiologies.