A defoliant is a toxic chemical agent used to remove leaves. Defoliants are classified into 6 types (purple, pink, green, blue, white and orange). From 1962 to 1971, due to removing leaves and securing their ability to see, the U.S. Army Chemical Corps veterans handled and sprayed defoliant in Vietnam. This resulted in exposure to Agent Orange and its contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin). This agent induces many medical problems in humans. Since 1992 in Korea, exposure to defoliants have given rise to several problems. However, there were few reactions due to the lack of data, social apathy, and international relationships. In this article, we review characteristics and diseases related to defoliants. (Korean J Dermatol 2011;49(10):863∼871)