Isopropylantipyrine is one of the pyrazolon derivatives which are nonsteroidal anti-inflammatory drugs (NSAIDs) with potent antipyretic and pain-relieving properties. It has been known that pyrazolon-hypersensitive patients, in contrast to ASA-sensitive patients, could safely use other NSAIDs. We describe two Korean patients with isopropylantipyrine hypersensitivity without ASA/NSAID hypersensitivity.