A case of urticaria due to menthol is reported in a young girl exposed to mentholated cigarettes, cough drops, aerosol room spray, and topical mentholated medicaments. The etiology was suggested by the history of exposure and was established by the results of oral challenge to menthol. A urticarial reaction and a fall in the total number of circulating basophils following menthol challenge were considered diagnostic of hypersensitivity. Skin tests to menthol were not diagnostic. Direct in vitro basophil degranulation tests to menthol showed a significant degranulation of basophilic leukocytes. This second case of menthol urticaria suggests a higher incidence than was previously considered.