This study was conducted in the Dawuro Zone of the Southern Nations, Nationalities and People Region. The specific study sites were Mareka and Tocha districts which were randomly selected from the Zone. The objective of the study were to determine the impacts of bovine trypanosomosis on cattle herd size and composition, milk yield and reproductive performances of cattle. Known tsetse infested areas, Tercha and Lala Kebeles were selected from Mareka and Tocha districts, respectively. As a control, known tsetse free area, Docha Kebele, was selected slected from Mareka District. A total of 52 households were selected randomly from each Kebele that made a total sample size of 156 households. A structured questionnaire was prepared and one visit interview was carried out to collect data about on socio-economic characteristics, farming system characteristics, cattle herd size and composition, milk yield and reproductive performances of cattle, major cattle health problems and mortalities. In addition, a total of 30 pre-partum cows were selected (10 from each Kebele) for a postpartum follow-up study, which lasted for about six months (October 2006-March 2007), to collect data on daily milk yield and the occurrence of first postpartum observable heat. Data collected were analyzed using descriptive statistics and independent t-test. The results showed that the most important cattle health problem identified were trypanosomosis and blackleg in tsetse challenged and free areas, respectively. Cattle herd size did not different significantly (p>0.05) between tsetse challenged and free areas. However, the average number of lactating pregnant (p