We inuestiqatedthe knowledge, attitude, and behavior about Dengue hemorragic fever prophylaxis among persons in Hoa Loi commune, Chau Thanh district, Tra Vinh province in July-2005 through a questionaire: 82% have heard about the disease, 69, 2% recognise the differrent symtoms, 78, 4% know about the vector and 98, 8% know one or many ways to avoid the disease.