Gypsy moth caterpillar dermatitis is a pruritic, papular, urticarial eruption on exposed skin that occurs most commonly after direct contact with the first instar larva of the gypsy moth (Lymantria dispar). We present two case reports to illustrate its clinical and histopathologic features. Both cases occurred during the spring of 1990 and coincided with the greatest infestation of L. dispar in the Northeast to date. The pathogenesis of this distinctive gypsy moth dermatitis most likely involves histamine release by the caterpillar and a delayed hypersensitivity reaction in its host.