After coronary artery bypass graft surgery, most patients will have a small, unilateral, left-sided pleural effusion, and approximately 10% of patients will have a larger effusion. These large effusions can be separated into (1) early effusions occurring within the first 30 days of surgery that are bloody exudates with a high percentage of eosinophils, and (2) late effusions occurring more than 30 days after surgery that are clear yellow lymphocytic exudates. The primary symptom of pleural effusion after coronary artery bypass graft surgery is dyspnea; chest pain and fever are uncommon. Most patients with large pleural effusions after coronary artery bypass graft surgery are treated successfully with one to three therapeutic thoracenteses.