A census of all Listeria monocytogenes isolates was made in 1986 by the microbiologists of 75% of the French hospitals. 811 cases were registered giving a yearly incidence rate of 14.7 cases/million population instead of 11.3 cases/million population registered in 1984. The cases are classified in perinatal cases (positive culture for L. monocytogenes from the mother, the child or the placenta) and non perinatal cases (all the others). The increase between 1984 and 1986 is mostly due to the fact of the non perinatal cases. A seasonal increase was observed in May-June-July of 1986. Case fatality rate observed was 29%; therefore the two classes have basically the same rate.