Trypanosomosis in animals is caused by extracellular flagellate protozoan parasites under the genus Trypanosoma of Family Trypanosomatidae. In cattle there are different species of trypanosome causes the disease these are Trypanosoma congolense, Trypanosoma brucei brucei and Trypanosoma vivax (Uilenberg and Boyt, 1998) which transmit cyclically by Glossina spp. ( Tse tse flies) in humid and semi- humid zones in sub- Sahara Africa in an area of 10 million Km2 (Black and Seed, 2002). T. vivax and T.congolense can be transmitted mechanically by biting flies such as Tabanids and Stomoxys (Desquesenes and Dia, 2003a, Desquesenes and Dia, 2003b). Abdalla et al. (2005) reported that out-side the tse tse belt T. vivax is the causative agent of the disease in cattle in central Sudan during dry and wet seasons. In Kassala state, the incidence of the disease was 0.6% between years 1994 and 2003 (Salih et al., 2005). This work reports the prevalence rate of bovine trypanosomosis in Kassala State during 2007-2008 and the role of the seasonality in the incidence of the disease.