A 24-years-old man was referred to our University Hospital because of one and a half-year history of disabling symptoms related to physical exertion. Multiple small round-shaped wheals with severe itch were induced by exercise, warmth and psychological stress. These symptoms were resistant to histamine H1-receptor antagonists. Similar eruptions were induced by sauna-bathing, and skin test with autologous sweat showed a flare and wheal reaction. Incubation of his peripheral-blood leukocytes with partially purified sweat antigen evoked marked histamine release, indicating that he has been IgE-sensitized to an antigen(s) in human sweat. Specific immunotherapy using partially purified sweat antigen was performed every other week. Both pruritus and wheals improved gradually, and the reactivity of his peripheral blood leukocytes against sweat antigen decreased as immunotherapy was proceeded. Specific immunotherapy using sweat antigen may be valuable for patients with cholinergic urticaria with type I hypersensitivity to sweat antigen(s).