Idiopathic erythermalgia during early childhood and adolescence is characterized by red, congested, burning pain of the lower extremities provoked by exercise or exposure to warmth. The clinical symptoms of idiopathic erythermalgia in a young woman and her mother are described. Histopathologic and immunofluorescence findings in biopsy specimens of affected areas of skin were consistent with a nonspecific inflammatory process. The condition was completely refractory to any treatment. Even the long-lasting relief of pain with one low dose of aspirin, which is a prerequisite for the diagnosis of thrombocytemic erythromelalgia, was lacking. Idiopathic erythermalgia appears to be a separate clinical entity and congenital disorder.