Our aims were to identify the range of blood pressure values during the first postnatal week in infants born between 23 and 25 weeks postmenstrual age who were not considered in need of treatment for hypotension, and to describe the clinical course of these untreated infants compared with those who were treated for hypotension. We reviewed retrospectively the charts of 142 consecutive inborn infants over a 6-year period. For 86 infants who survived the first postnatal week without being treated for hypotension, the mean arterial pressure (MAP) increased 0.3 mm Hg/h during the first 24 hours, 0.1 mm Hg/h from the 25th to the 48th hour, and then stabilized for the remainder of the week. MAP values < or = 25 mm Hg were not uncommon and were not associated with apparent consequences. Thirty-five infants treated for hypotension differed significantly from untreated infants in several clinical variables present at birth, suggesting a different degree of fetal compromise. Treated infants were less likely to survive (43 versus 85%; P < 0.001) or survive without a major morbidity (29 versus 53%; P = 0.013) than untreated infants. It was not apparent from our data that the treatment of hypotension was helpful.