Twenty-one children having atopic dermatitis, underwent skin tests with 1:1,000 methacholine; 16 demonstrated the delayed-blanch phenomenon. Seven were studied for skin temperature responses and compared with seven nonatopic children. Atopic children have a lower basal skin temperature than nonatopic children. Exposure to a cold environment produced more rapid cooling of the fingers and toes of the atopic children. Some alterations in cutaneous vascular responsiveness are present to development of severe dermatitis.