['To determine whether surfactant administration affects cerebral and systemic hemodynamics and gas exchange in very low birth weight infants and to determine the predominant factor influencing changes in mean cerebral blood flow velocity (mCBFv) after surfactant instillation.', 'Fourteen very low birth weight infants with respiratory distress syndrome had continuous monitoring of mCBFv, Paco(2), mean arterial blood pressure (MABP), and Pao(2) before, during, and after the second dose of surfactant. Peak values and relative changes of the 4 variables for 45 minutes after surfactant were calculated. Logistic regression was used to determine the predominant factor influencing changes in mCBFv after surfactant.', 'Birth weight was 832 +/- 162 grams and gestational age was 25.7 +/- 1.5 weeks. The time from birth to monitoring was 6.9 +/- 1.0 hours. Mean CBFv increased 75.7% +/- 51.6% after surfactant and peaked at 14.4 +/- 5.9 minutes. Paco(2) was highly associated (OR=107.3, P <.0001) with mCBFv; as Paco(2) increased, mCBFv increased. In contrast, MABP (OR=6.7, P=.047) had less impact on mCBFv. Pao(2) was not associated with mCBFv.'] Does surfactant administration acutely affect cerebral and systemic hemodynamics and gas exchange in very-low-birth-weight infants?