ABSTRACT: A comparative case-control study to assess the determinants of Community Health Agent (CHA) functionality was done in two Arsi districts, in mid-southern Ethiopia. This was a census study which was conducted by interviewing 347 CHAs from a structured questionnaire. The objectives were to describe the situation of the CHAs trained up to the end of 1987, and to elucidate determinants of CHA functionality by comparing the attributes of functional CHAs (cases) with that of the nonfunctional ones (controls). The findings revealed that only 25.8% of the CHAs interviewed were performing 50% or more of the activities mentioned in their job description. It also revealed a point prevalence attrition rate of 45%. Comparing cases and controls showed a strong association between functionality and community support for the CHAs (RR = 72.4 with 95% CI 35 - 153). Association was also found between functionality and supervision by health institutions, presence of health posts, provision of stationary drugs and to the CHA, and establishment of an active health committee. These findings emphasize the importance of provision of proper community and health system support for the success of the community health services program.