The incidence of complications following the insertion of central venous catheters in acute myocardial infarction was determined in 240 cases. All catheters were inserted percutaneously. Infection occurred rarely: one patient was successfully treated for Staphylococcus aureus septicemia and one for a local infection. Phlebitis occurred in 16% of cases. Only four patients had symptomatic subclavian vein thrombosis, yet routine phlebograms in 20 consecutive patients showed four instances of asymptomatic axillary vein thrombosis. Anticoagulant therapy was of no value in preventing thrombus formation.