Methods for establishing the diagnosis in cholinergic urticaria are reviewed and compared. Provocation by exercise or hot bath is more effective than local provocation by intradermal tests. Of the intradermal tests, responses to nicotine acid tartrate and acetyl β methylcholine chloride are positive only in patients with the more severe, readily induced eruptions. Furthermore, intradermal testing is not always reproducible in the same patient. In our patients, exercise proved the simplest, most effective diagnostic test.