A total of 284 general practitioners (GPs), paediatricians and doctors of public vaccination centres (DPVC) were interviewed to investigate their willingness to immunize children with compulsory (diphtheria-tetanus, oral polio) and non-compulsory (measles, pertussis) vaccines in the presence of 19 different medical histories. We observed a reluctance to immunize in the case of false contraindications, a lack of information mainly about non-compulsory immunizations, and doubts about the real contraindications to polio, measles and pertussis vaccines. The frequency of correct answers to the question posed was significantly higher in the group with less than 20 years of experience, and the DPVCs proved better informed about immunization. However, the crucial role played by the GPs and paediatricians' advice can prejudice the correct use of active immunization.