Beginning in March 1995, in the adjacent provinces of Benevento and Campobasso in Southern Italy, we carried out a sentinel, paediatrician-based surveillance on pertussis, measles, rubella and mumps with the aim of evaluating the health impact of new vaccination programmes and the objectives of describing the time-space trends and estimating the effectiveness of new vaccinations. The study population consisted of 16,500 children attended by 25 paediatricians. The estimated effectiveness of vaccines for pertussis, measles and rubella were close to the expected values, although a very low effectiveness was calculated for the mumps vaccine. The comparison among children vaccinated with various strains showed a diseases odds ratio of 2.5 for the children vaccinated with Rubini strain. The effectiveness of this strain has to be verified in more rigorous settings.