On histological examination, an epidermolytic hyperkeratosis was observed adjacent to follicular papules on the back of a 53-year-old man. It has been reported that incidental epidermolytic hyperkeratosis occur either within various lesion (epidermal neoplasm, melanocytic neoplasm, scars, and inflammatory conditions) or in the normal skin adjacent to the lesion. This patient participated in the Vietnam War for 2 years, and had had contact with defoliants. He was treated for multiple peripheral neuropathies and cerebral infarcts. In keratinocytes, 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD; Agent Orange) contained in defoliating agents is associated with altered patterns of keratinocyte differentiation. So, as a cause of incidental epidermolytic hyperkeratosis, defoliant contact could be suspected.