In Italy, systematic mandatory tetanus immunization of children started in 1968. In 1989, immunity against tetanus was assessed in a random sample of 758 healthy subjects aged 3-20 y, from four Italian cities. There were 257 subjects 3-5 y old all residing in Southern Italy and 501 subjects 11-20 y old from both the South and North. The overall prevalence of non-immune subjects was 19.1%, without difference by sex. The rates of subjects lacking protective antibody titres was 25.3% in children 3-5 y old (all coming from South and the islands), 11.5% in those 11 y old, and 18.9% in the 18-20 y age-group, respectively. Subjects 11-20 y old residing in the South and the islands were more likely to be non-immune that those residing in the North (20.2% vs 6.0%; P < 0.01). Socio-demographic indicators such as lowest paternal education and largest family size were both unassociated with lack of protective antibodies. These findings indicate that an high rate of children in South of Italy do not have protective antibody levels, probably as consequence of lack of compliance with the vaccination programme. More efforts should be addressed to decrease geographical inequalities in the delivery of health care.