A 36-year-old HIV-infected man admitted with a possible pyelonephritis of the left kidney and a 3.5 cm thrombus of the left renal vein developed sudden onset of dyspnea. Multiple cavitating nodules revealed under CT were aspirated yielding purulent fluid. MRSA isolates, from both the lung and blood had identical susceptibility patterns. The patient failed to respond to antibiotics until intravenous heparin was begun.