A 58-year-old woman presented with dyspnea and arthralgia. Five months earlier, the findings of a chest radiograph were normal and showed no pleural effusion. A chest radiograph at the time of presentation and a subsequent CT scan found moderate-sized bilateral pleural effusions with no evidence of pleural thickening (Fig 2). Laboratory investigations showed raised levels of rheumatoid factor (148 international units/mL; normal level, < 10 international units/mL) and anti-cyclic citrullinated peptide antibody (55 units/mL; normal level, < 7 units/mL), a peripheral eosinophilia, and a raised erythrocyte sedimentation rate (31 mm/h). The pleural fluid appeared milky with a raised cholesterol concentration (460 mg/dL [11.9 mmol/L]). The results of laboratory investigation for chylomicrons were negative. Thoracoscopy of the right pleural cavity showed no gross pleural thickening, and biopsy revealed chronic inflammatory cell infiltrates including lymphocytes, eosinophils, and plasma cells. Therapy with prednisone and methotrexate were started for the treatment of rheumatoid arthritis, and the pseudochylothorax was stable at the 6-month follow-up.