We report allergic sialadenitis as a novel side-effect of naproxen, a non-steroidal anti-inflammatory drug (NSAID). Bilateral swelling of the major salivary glands and a rash occurred a few days after the patient had taken the drug. High-dose systemic corticosteroid therapy was required to control the disorder. Because the salivary gland swelling was not initially recognized as an adverse drug reaction, further doses of naproxen were given on two occasions, with similar results.