OBJECTIVE: Neonatal tetanus is an infection with high mortality, constituting a problem in underdeveloped countries, where there is faulty prenatal attendance. In spite of this and of the decreasing incidence of the disease in the state of Rio Grande do Sul, we report a case of neonatal tetanus identified in 1997. METHOD: We interviewed the infantacute;s mother and verified her vaccination history. We conducted a clinical examination of the newborn, anaerobic culture of umbilical stump and review of medical records. We also reviewed the literature and verified the epidemic profile of neonatal tetanus in Rio Grande do Sul.RESULTS: Healthy mother, with complete outline of tetanus vaccination 4 years ago, prenatal uncomplicated and hospital delivery. Family of good socioeconomic level, differing from the other cases notified in the State, in that most did not have prenatal care nor hospital delivery. The patient is a boy. In the 24th day of life he presented fever, cyanosis, lower and upper limbs muscle hypertonia and opisthotonos episodes. An anaerobic culture of the umbilical stump grew Clostridium tetani. He was treated with penicillin G, gentamicin, sedation and tetanus immunoglobulin. He left hospital in good conditions.CONCLUSIONS: Faulty prenatal care in underdeveloped countries is the largest risk factor for high incidence of this disease in these areas. However, in pregnant women with good socioeconomic level and prenatal care, as in the case described here, this diagnosis should not be excluded if there are suggestive signs of it.