• We studied 49 consecutively admitted infants of less than 34 weeks' gestation to analyze the role of several maternal, intrapartum, and neonatal factors associated with the occurrence of periventricular-intraventricular hemorrhage (PIVH). To detect PIVH, ultrasound studies were performed every eight hours during the first three days of life and every 12 hours during the following four days. In 20 infants (41%) PIVH was detected. Of these 20 cases, 30% were diagnosed immediately after birth and 55%, 70%, 90%, and 100% after 24,48,72, and 108 hours, respectively. Hypoxia, hypercapnia, and acidosis were the most important factors associated with the development of PIVH. Hypothermia was also an antecedent. Suctioning, serum osmolality, weight loss, transfusions, pneumothorax, patent ductus arteriosus, and bolus infusions with sodium bicarbonate were not associated with the onset of PIVH.