Percutaneous Silastic catheters (PSCs) are used in premature infants to deliver total parenteral nutrition. We report two cases in which migration of the catheter into the right atrium resulted in rapid onset of shocklike symptoms. Pericardial effusion and tamponade were diagnosed by echocardiography. Subxiphoid pericardiocenteses were performed, with immediate clinical improvement. In both cases, fluid withdrawn from the pericardial space was analyzed to be hyperalimentation and intravenous fat emulsion. Pericardial effusion and tamponade should be suspected in any infant with a PSC line in place who develops sudden onset of shocklike symptoms.