Selected growth and developmental parameters were monitored in each facility to determine differences in patient medical progress between the two designs. Discharge weights, lengths and head circumferences were compared with those taken at the time of admission as indices of overall growth in body mass and stature during hospitalization. Similarly, respiratory and nutritional parameters were monitored as indices of developmental progress. Respiratory data collected for comparison from the two units included conventional mechanical ventilation times, continuous positive airway pressure days, total apnea events, apnea events per day and days requiring caffeine administration. Apnea events and caffeine use were compared in more apnea-prone infants with gestational ages less than or equal to36 weeks. Nutritional parameters recorded as indices of gastrointestinal maturation included days on total parenteral nutrition (TPN) and intervals (days) to enteral nutrition. TPN data were collected from infants in both units with LOSs greater than or equal to14 days to eliminate bias from ‘short-stay’ subjects who did not require supplemental intravenous nutrition.