The focus of the study is on comparing health care programs that provide free ARVs in public health care settings in Tanzania and Zambia. The views of health care professionals and patients from vulnerable populations will be sought. Health planners have committed to providing free ARVs through public health care facilities with the explicit goal of improving access to treatment for vulnerable populations. One aim of this project will be to evaluate if providing free ARVs is enough to reach this goal. We aim to describe and define other formal and informal costs related to access and determine the extent to which they may contribute to inequitable access among vulnerable groups. Our ultimate aim is to contribute to the improvement of equitable access to ARV treatment in the countries concerned, as well as to provide insights and learning opportunities for sub-Saharan Africa in general.