Several nonsteroid antiinflammatory drugs (e.g., benoxaprofen, carprofen, and piroxicam) are known to induce photosensitivity reactions, but this has not yet been documented for ibuprofen. We observed a photosensitivity reaction in a patient treated with an oral ibuprofen preparation. This patient had a lowered minimal erythema dose for UVA but not for UVB after oral administration of ibuprofen. Results of a photopatch test with the drug were negative. In vitro UVA irradiation of human erythrocytes in the presence of ibuprofen caused ultraviolet dose-dependent phototoxic hemolysis.