[en] Radioactive tracer studies are a sensitive means to detect occult pulmonary aspiration of gastric contents. A complication of diagnostic endoscopy is aspiration of contents even in fasted patients. The authors have studied 21 hospitalized patients who underwent elective endoscopy (END) for suspected UGI pathology. Fifteen minutes before END, and prior to pharygeal anesthesia, 1 mCi Tc-99m-sulfur colloid, added to the usual 30cc of simethicone routinely administered before END, was given orally. END was performed as usual and 2 hours later anterior 100,000 count images of the chest were obtained. All the studies were interpreted without history or clinical information. Fever developed within 24 hours (and septic shock in 1) in both patients with positive studies while no fever occurred in the remaining patients with negative studies (rho<.001). The authors conclude that oral radionuclide pulmonary aspiration studies may; detect aspiration not recognized by the endoscopist, reveal evidence of aspiration that preceeds adverse clinical signs and symptoms, and be influenced by systemic pre-END drugs known to affect GI secretions and motility