Among the various complications of central venous catheterization, extravsscular migra tion of the catheter during fluid therapy is a rare condition to be encountered. We experienced a case in which an uneventful, successful insertion of subclavian catheter was followed at greater than 33 hours by massive mediastinal and bilateral pleural effusions, which resulted in hypotension, severe dyspnea, and cyanosis. The symptoms were re- lieved immediately after the bilateral thoracostomy and removal of the subclavian catheter. The chemical assay of the effusion was revealed glucoae-rich fluid given exogenously. The inferred cause was that postoperstive extravascular migration of the subclavian catheter probably resulted from both intensive respiratory physiotherspy and movement. We conclude that, although the successful placement of central line may be confirmed on insertion, a continuous reexamination of both function and location of the line is necessary to avoid the hazards of delayed diagnosis.