We have presented a case of tension hydrothorax that developed after hyperosmolar hyperalimentation fluids were infused into the pleural space through a misplaced jugular venous line. The hyperosmolar state of the pleural fluid appears to have played a prominent role in the development of the tension hydrothorax. We believe there is a risk of tension hydrothorax in any clinical situation in which the pleural fluid glucose concentration is significantly higher than the serum concentration.