Aspirin is one of the world's most commonly used medications and its use benefits many diverse conditions. Adverse reactions, however, are relatively common as well. Hypersensitivity to aspirin can be manifested as acute asthma, urticaria and/or angioedema, or a systemic anaphylactoid reaction. We report 3 cases in whom aspirin was indicated for secondary prophylaxis of myocardial infarction but in whom a remote history of an untoward reaction to it prevented its initial use. These patients all underwent further evaluation of their pulmonary and allergic history and all 3 were challenged with aspirin. Two patients were found not to be sensitive and started on aspirin, the other had a classic asthmatic reaction to the drug and was successfully desensitized to aspirin allowing for its use.