A general opinion is that compliance with the compulsory immunization programme of children is excellent in Italy. We have studied antitetanus immunity in relation to vaccination history in a sample of 444 school children born between 1977 and 1981 in a district of Naples. Information on vaccination history was collected by interviewing the parents and validated using the official vaccination certificates. Titration of antibodies against tetanus was carried out by the immunoenzymatic method. 0.9% of our study subjects had not been vaccinated at all and only 21.2% had received 4 vaccine doses. In 18 children the presence of antitetanus antibodies was not detected; 14 of them had received one or more doses of vaccine. The lack of compliance with the vaccination programme was associated with a remarkable delay in administering the tetanus vaccine. In the population reported here, the percentage of subjects only partially covered is higher than that found in other regions of Italy.