The functional status of community health workers in many instances rapidly drops following their completion of training. The objective of this field trial was to determine the effect of a refresher course and monthly supervision on the health service activities of community health agents (CHAs). A total of 102 CHAs located in two districts of the southwestern Ethiopian region of Illubabor who were performing at least one activity as specified in their job description were identified. All communities in which these CHAs worked were visited and baseline input to enhance community involvement was provided. Following these visits one of the districts was randomly selected and all CHAs in that district were given a refresher course and provided monthly supervision (intervention group). The CHAs were observed monthly for six months in order to collect data on 13 health service activities. At the onset there were no statistically significant between-group differences among the individual and composite activities performed. A group by time analysis found that the composite functional status score (p<0.0001) and 10 of 13 activity scores (p<0.05 to 0.0001) were signrficantly higher among intervention group CHAs at three and six months following the onset of the trial. These differences are attributed to the refresher course and regular supervision which, in turn, enhanced community support.