Abstract: In both adults and children, weight loss is one of the major complications of HIV infection and constitutes a factor of bad prognosis. The aim of this study was to assess the prognosis value of Body Mass Index and CD4 cell count among HIV sero-positive adults attending Academic Model for Prevention and Treatment of HIV/AIDS (AMPATH) outpatient clinic, to improve the nutritional management of HIV-infected patients. A prospective cohort study of 497 patients infected with human immunodeficiency virus in Chulaimbo hospital, Kenya assessed the nutritional status. Evaluation of nutritional status was done using anthropometry and immune integrity by use of CD4 cell count. Among the 497 patients recruited the Male: Female sex ratio was 1:4 and mean age: 39.0±10.5 years). The men were leaner (BMI = 20.5kg/m2 in men) than the women (BMI = 21.7kg/m2) and patients with a CD4+ T cell count < 200 cells/mm3(category three) tended to have the lowest mean values for all anthropometric measurements. 79.7% had normal nutritional status with a mean CD4 cell count of 431 cells/mm3. Malnutrition was observed among patients in all the three categories (mild, 20.8%, moderate, 43.6% and severe, 35.6%). Determining the BMI in HIV sero-positive adults could constitute an objective and quick method for assessing the prognosis of malnutrition. Given its high frequency, malnutrition should be prevented, detected, monitored and treated from the early stages of HIV infection among patients attending AIDS clinics in order to improve survival and quality of life. Insights were gained about relative value of using various measurements to assess nutritional status of HIV-infected populations.