A 64-year-old man presented with worsening dyspnea on exertion and hemothorax of the left chest 7 days after discharge from the hospital on ticlopidine and aspirin after coronary stent placement to his left circumflex artery. He had suffered traumatic rib fractures to the seventh, eighth, and ninth left ribs 28 days before this presentation and 21 days before starting the ticlopidine. Results of chest radiography at discharge 7 days earlier while on aspirin and after brief IV heparin had been negative except for minimal atelectasis and rib fractures barely visible on posteroanterior view. The delayed hemothorax had lowered the peripheral blood hematocrit to 23% and required tube thoracostomy drainage and blood transfusion. The delayed traumatic hemothorax in this case occurred on treatment with ticlopidine and did not recur with continuation of aspirin alone.