Abstract: Immunodeficiency virus co-infection rate in North-Eastern Nigeria. Two hundred consecutively recruited HIV/AIDS patients comprising 69 males and 131 females were screened for Hepatitis B surface antigen using ELISA. The biodata of the patients were obtained. Out of the 200 HIV/AIDS patients tested, 30 were positive for Hepatitis B surface antigen giving an overall co-infection rate of 15.0% of the 69 males, who had HIV/AIDS, 13 (18.8%) were Hepatitis B surface antigen positive, while 17 (13.0%) of the 131 females with HIV/AIDS were positive. Co-infection rate was highest in the 30-39 years age group (46.7%), while no case of co-infection was found in the 10-19, 50-59 and 60-69 years age groups. This study confirms a high co-infection rate of Hepatitis B virus infection in patients with HIV/AIDS. Therefore, there is a need to screen patients with HIV/AIDS for Hepatitis B virus infection.