Many immunization programs in developing countries arr now undergoing a period of rapid utilization. Innovative strategies, such as immunization holidays, are being tried. Political commitment and enthusiasm are high. There is a strong desire by health professionals to protect the lives of many children from the untimely death and/or disability resulting from infectious diseases preventable by vaccination. Evaluation of an immunization program can benefit other elements of the health system, particularly those that are not amenable to objective evaluation as immunization. In this case, immunization can serve as an indicator of the overall performance of the health system. The problems revealed by evaluation of the immunization program could therefore be taken as problems generic to the health services as a whole. In remedying the problems for immunization, approaches that would improve the health services as a whole should be sought. The primary purpose of this study was to determine the intrinsic and extrinsic factors contributing to coverage and participation rates of the vaccination program in Arssi, Ethiopia. vaccination program participation is relatively easy to estimate, although its importance should not be overemphasized as the primary goal of immunization programs is the reduction in mortality, morbidity, and disability resulting from infectious diseases preventable by vaccination. The survey questionnaire, adopted by the World Health Organization (WHO), was one of the instruments used for this project. Results of the evaluation in 1988 showed that only 66.5% of the children surveyed were fully vaccinated, while 26.9% were partially vaccinated, and 16.6% were not vaccinated at all. Comparisons of the survey results between the years 1983, 1985, and 1988 was made to determine whether or not there was improvement in vaccination coverage between the years. Decisions about the differences of the survey results in population proportions between the years were based on whether or not the differences were scientifically significant, leading us to the rejection of the null hypothesis of no difference (zero), and whether or not the results were scientifically important (whether or not the results showed an increase in vaccination coverage). An increase in usage rate was noticed more in 1988 than the previous survey results of 1985 and 1983. Mothers or guardians were asked about the possible reasons of immunization failures when their children or themselves were found partially or not-vaccinated. The reasons included such facts as lack of information, lack of motivation, obstacles/barriers, and wrong/improper vaccination techniques. Based on the literature review and the survey results, recommendations were made to help correct the observed problems and achieve a higher level of vaccination coverage.