Background: Although topical application of aluminium chloride is the most common measure against axillary sweating, severely affected patients often undergo surgical procedures that are expensive and may have considerable side effects. Recently botulinum toxin A (BT-A) has been reported as a potentially effective antihyperhidrotic agent. Objective: Our purpose was to determine the therapeutic strength, safety, and mode of application of BT-A in severe axillary hyperhidrosis. Methods: Intradermal injection of BT-A (Dysport) was given in an open left-versus-right side trial with each patient being his own control for initial efficacy, followed by treatment of the contralateral side. Results: Seven days after initial treatment sweat production fell to below 10% of the untreated contralateral axilla as determined by gravimetry. Satisfaction was rated unanimously as “very good,” the highest of 5 rankings. No side effects such as skin irritation or muscle weakness were noted in any patient. Conclusion: Intradermal injection of BT-A is a potent and well-accepted therapeutic option in patients with recalcitrant axillary hyperhidrosis. (J Am Acad Dermatol 1999;41:987-90.)