The recent use of soft catheters made of silastic polymeric silicone or polyurethane has decreased the incidence of perforation of great veins or right-sided heart chambers but has not eliminated it as had been hoped. Two premature infants who presented with cardiac tamponade more than 24 hr after the insertion of a 23-gauge silastic catheter for total parenteral nutrition (TPN) administration are described. In one infant, bilateral hydrothorax preceded the occurrence of cardiac tamponade. Osmotic injury to great vessels and/or myocardium seems to be the common mechanism but which these complications of intraluminal catheters are produced. Review of the pediatric literature revealed a proportion of low birth weight infants among the reported cases. Despite a prohibitively high mortality rate, early recognition can prevent a fatal outcome.