Cost/benefit analysis could be an important approach in improving the decisional process in public health. We used the direct benefit/cost analysis and clinical cases of measles, acute hepatitis B, pertussis, and tetanus notified in North-West Romania to evaluate the results of immunization programs against such diseases. The numbers of potentially occurring cases of diphtheria were evaluated based on incidence data published in literature. The Excel under Windows 2000 software has been used to process the data. The benefit/cost rates of mass immunization programs were of 5.5 for measles, 9.5 for acute hepatitis B, 5.8 for pertussis, 71.1 for tetanus and 192.5 for diphtheria. The rate was low for measles because of the occurring outbreaks, for pertussis because of prevailing mild clinical cases, and for hepatitis B because only clinical cases were counted. The immunization programs against tetanus and diphtheria had the most relevant economic advantages.