Magister Public Health - MPH / Background: The goal of ART therapy is sustained viral load suppression with good immunological and clinical response. This optimal response to therapy results in the prevention of emergent ART drug-resistant mutations, decrease morbidity, and AIDS-related mortality and sustained retention on ART. Kenya, like most countries in Sub-Saharan Africa, has scaled-up the use of ART and is currently implementing a “Test and Treat” strategy in which any client identified and confirmed with an HIV diagnosis is initiated ART. Few studies have been carried out to ascertain the response of HIV patients initiating treatment in resource-limited settings. Moreover, it has been demonstrated that a certain proportion of patients fail to adequately respond to therapy and therefore require therapy modification. Aim: To assess treatment outcomes and calculate retention of HIV infected adult patients’ (15 years and above) initiating ART at Kakamega County General Hospital. The primary study outcome was the treatment outcome of patients-initiated ART two to three years prior to the study; while, the role of WHO criteria for screening treatment failure was assessed as a secondary outcome. Methods: This was a retrospective cohort study in which patients initiating ART between June 2014 and March 2015 were followed up until they were censored or study closed in August 2017. 284 patients were enrolled in the study after accurately matching information in their clinic files and the electronic medical record. Data were collected from patient records using a chart abstraction tool and transferred to an Access database from where the cleaning and validation of entries were done. Data from Access was transferred to STATA 15.1 for analysis. Descriptive statistics and inferential statistics were then performed to answer the research questions.