Summary Over a 3½ year period, from 1991 to 1994, we detected contact allergy to tioconazole in 72 patients by epicutaneous testing. During this period, tioconazole was included in the standard series of epicutaneous tests. Except for the first 6 months, the incidence of positive patch test reactions to tioconazole was over 1% of patients tested for contact allergy. As well as those tested with the standard series, 18 additional patients with tioconazole allergy were detected by direct testing with an imidazole patch test series. Of the various imidazole derivatives, tioconazole was the most important contact allergen. About half of patients with contact hypersensitivity to tioconazole, had additional contact allergies detected by the standard series. Men and women were equally affected. The present study suggests that tioconazole is an important contact allergen, which should be included into the patch test series in countries where it is used as a topical antifungal agent.