Exercise-induced anaphylaxis (EIA) is well known and may be food-dependent. We describe a patient with a history of anaphylaxis during exercise after taking nafylpropion acid (Naprosyne), a nonsteroidal anti-inflammatory drug. An exercise-challenge test after Naprosyne intake induced bronchoconstriction. The combination of history and challenge tests suggests that intolerance or allergy to drugs may present as EIA.