Deoxynivalenol (also known as Vomitoxin), an epoxy-sesquiterpenoid, is a type B trichothecene and an inhibitor of DNA and RNA synthesis. This mycotoxin occurs predominantly in grains such as wheat, barley, oats, rye, and corn, and less often in rice, sorghum, and triticale. The occurrence of deoxynivalenol is associated primarily with Fusarium graminearum and F. culmorum, both of which are important plant pathogens which cause fusarium head blight in wheat and gibberella or fusarium ear blight in corn. A direct relationship between the incidence of fusarium head blight and contamination of wheat with deoxynivalenol has been established. The incidence of fusarium head blight is strongly associated with moisture at the time of flowering, and the timing of rainfall, rather than the amount, is the most critical factor. However, increased amount of moisture towards harvest time has been associated with lower amount of vomitoxin in wheat grain due to leaching of toxins. Furthermore, deoxynivalenol contents are significantly affected by the susceptibility of cultivars towards Fusarium species, previous crop, tillage practices, and fungicide use. It occurs abundantly in grains in Norway due to heavy rainfall.