Background: Respiratory tract infections with more than one organisms are common in immunosup pressed patients, especially those who are Human immunodeficiency virus (HIV) positive. Mycobacterium tuberculosis and Streptococcus pneumoniae are the most important and dangerous pulmonary bacterial pathogens with global impact. This present study assessed the prevalence of Streptococcus pneumoniae and Mycobacterium tuberculosis co-infection and associated risk factors among HIV infected Adult Patients on Highly Active Antiretroviral Therapy (HAART) attending the