In Uganda, the Iteso live mainly in Teso sub-region, i.e., the districts of Amuria, Soroti, Kumi, Katakwi, Ngora, Serere, Pallisa, Bukedea and Kaberamaido, as well as in the districts of Tororo and Busia. They number about 3.2 million (9.6% of Uganda's population). Until 1980, they were the second largest ethnic group in Uganda. As of 2002 they were the fifth largest but this has remained questionable especially since there has never been any genocide that could have massacred more than a half of the Iteso populace. Most of the Iteso therefore contend that they are still the second largest ethnic group in Uganda. In fact the figure portrayed by UBOS is rather a political statement than an accurate recording of the Iteso in Uganda. Most Teso elites continue to argue that, since the national budget is disbursed based on population numbers, some individuals in government often manipulate these figures to suit their political interests and as such, as long as the current NRM government continues in power, the national population census figures can never be accurate but rather will continue to serve selfish political interests in order to justify why some areas in the Country like Teso, remain poor and underdeveloped. 
The Iteso in Kenya, numbering about 578,000, live mainly in Busia county. The Kenyan Teso people are an extension of their Ugandan counterparts in that they were merely separated by the partition of East Africa during the historic scramble and partition of Africa just like the Maasai of Kenya and Tanzania and the Oromo of Kenya and Ethiopia. They are among the Plain Nilotic groups closely related to the Turkana, Karamojong, Toposa and the Maa groups of the Maasai and Samburu. The prominent people in Teso include the current governor of Busia County, Hon Sospeter Ojaamong, Hon Albert Ekirapa, Ojamaa Ojaamong, Oduya Oprong, Pancras Otwani, educationists like Isogol Titus, Silvester Silver Omunyu and student leaders like Titus Adungosi,Odula Ongaria Meshack Patrick Emongaise and Samson Iliwa The Iteso people are located in Western Province of Kenya currently in Busia County which is in South of Mt. Elgon. Still, a large number of them inhabit parts of Bungoma and even Trans Nzoia Counties which are dominated by the Bukusu of the Luhya community. Teso people are the only Plains Nilotic people whose lifestyles underwent drastic changes. Having been pastoralists since time immemorial, these people are now the most successful farmers in both Western Kenya and Eastern Uganda. In recent years the people have changed much of their lifestyle. They used to exhume the dead after some time because of population pressure on their land and they no longer have bushes to dump the bones of people who died long time ago. Now they use cement graves -- a sign that they have embraced new ways of dealing with the dead. They believe in one God (Akuju/amsabwa) and also in life after death.
Northern and Southern Teso
Teso traditions relate that they originated somewhere in what is now Egypt in the area of Alexandra. They are believed to have descended from the Hebrew Joseph who had married a black Egyptian. Later when the Israeli slaves left Egypt for the promised land, the group followed the blue Nile river into Ethiopia. It is from here that they obtained the name Iteso, meaning we have seen. They saw a land, part of the promise to Jacob, the grand son of Abraham, it is a land divided by small rivers originating from the White Nile, theirs was the Upper Nile area. From the Ethiopian mountains is where they saw the land. They later migrated south West over a period of centuries. They were part of a larger group of Nilo-Hamitic peoples who include; the Masai and Turkana of Kenya, the Nyangatom of present day Ethiopia, Karamojong, the Topotha of South Sudan, all are they Ateker. The Ateker further split into several groups, including Jie, Turkana, Karamojong and Teso.
The Teso established themselves in present-day north-eastern Uganda, and in the mid-18th century some began to move farther south. During the course of this latter migration, conflicts ensued with other ethnic groups in the region, leading to the split of Teso territory into a northern and southern part. In 1902, part of eastern Uganda was transferred to western Kenya - leading to further separation of Teso.
Northern Teso occupy the area previously known as Teso District in Uganda (now the districts of Amuria, Soroti, Kumi, Katakwi, Pallisa, Bukedea and Kaberamaido). Southern Teso live mainly in the districts of Tororo and Busia in Uganda, and Busia District in Kenya's Western Province.
- Karp, Ivan (1978). Fields of Change among the Iteso of Kenya. Routledge; Reprint edition (2005). ISBN 0-415-32990-6.
- 2002 Uganda Population and Housing Census: Analytical Report (Uganda Bureau of Statistics)
- Mwakikagile, Godfrey (2009). Ethnicity and National Identity in Uganda: The Land and Its People. New Africa Press. ISBN 9987-9308-7-5.
- Shillington, Kevin (2005). Encyclopedia of African History Volume 1 A-G. New York: Routledge. pp. 1912 pages. ISBN 1-57958-245-1.