HIV infection is known to increase the risk of venous thromboembolism by 2 to 10 folds. Studies have included the traditional risk factors such as prolonged ill health, hospitalization, infection and the use of protease inhibitors as possible causes. HIV infection being a chronic inflammatory disease induces a derangement in the levels of positive and negative acute phase reactants which may contribute to endothelial cell dysfunction thus increasing thromboembolic risk. This study aimed to evaluate acute phase reactants antithrombin and plasminogen activator inhibitor-1 (PAI-1) as markers of increased predisposition to thrombosis in HIV infected persons and comparing their levels with D-dimer levels- a marker of fibrinolysis and with fibrinopeptides A and B- markers of thrombogenesis. The presence (or not) of asymptomatic thrombosis in both lower limbs of HIV infected persons using Doppler ultrasonography was also determTo document the presence of asymptomatic thrombosis in both lower limbs using Doppler ultrasound scan. Patients and Methods This was a cross-sectional study conducted on HIV infected participants and HIV negative control population. A total of 240 participants were recruited in the study. This included 80 persons in the control group and 80 persons in the HAART exposed and HAART naïve groups respectively. HAART exposed group were virologically suppressed at the time of the study. Investigations carried out included complete blood count, ALT, creatinine, CD4+ cell count, HIV RNA load. Antithrombin, PAI-1, D-dimer, fibrinopeptides A and B were measured using ELISA based technique.