The aim of this study was to evaluate the placental transfer of cefodizime (HR 221) in 28 women undergoing a cesarean section. After a single injection of 1 g cefodizime i.m., maternal blood, amniotic fluid and foetal cord blood samples were collected after 0.5 to 12 hours. The antibiotic assay was carried out by a microbiological procedure. The results showed a significant placental transfer of cefodizime with an early peak of 5.8 micrograms/ml at the 2nd hour in the cord blood and a progressive diffusion of the drug in the amniotic fluid until a maximal value of 9.9 micrograms/ml 11.5 hours after injection.