We describe the successful resuscitation of a very low birthweight infant after sudden deterioration caused by a massive pericardial effusion. The neonatal course of this 740 gm, 26-week gestational age infant had been complicated by moderate respiratory distress syndrome, apnea, and bronchopulmonary dysplasia. A Silastic catheter was placed percutaneously in the right axillary vein on day 6 of life and documented to be in the superior vena cava prior to continuous parenteral nutrition. On day 38, her cardiorespiratory status abruptly deteriorated, blood return could not be obtained from the central line, and it was removed. Chest radiograph and subsequent echocardiogram confirmed a massive pericardial effusion. Under echocardiographic guidance, an emergency percutaneous pericardiocentesis allowed aspiration of 23 ml of straw-colored fluid. Her vital signs immediately returned to normal and reaccumulation of the effusion did not occur. Despite the high mortality of premature infants from pericardial effusion as a complication of central venous catheterization, early diagnosis and prompt therapy can assure a good outcome. As a cause of sudden deterioration of very low birthweight infants, tamponade must not be forgotten, since it is now a rapidly treatable complication of central venous cannulation.