The aim of the study was to compare the placental transfer of tetanus toxoid antibodies (TTAB) and total IgG in Africa, where we had previously demonstrated a lack of transmission from mother to the newborn of measles antibodies. Two series of mother-child pairs, 45 in Paris and 134 in Libreville, Gabon, Central Africa, were measured after full-term pregnancies and normal deliveries. Means of ratios of cord/mother concentrations for TT AB and IgG were, respectively, 2.52 and 1.28 in Paris and 0.98 and 0.82 in Gabon. In 11 pairs from Libreville no TT AB were found in mother and cord blood, but in four other African newborns (3 per cent), the mother transmitted TT AB which were lower than protective level against tetanus. Other data (negative correlation between mother IgG and cord/mother ratio of corresponding TT AB concentrations, and better transmission of TT AB in the low range of maternal IgG) indicate that the limitation of active placental transfer of antibodies is related to the high maternal IgG level common in Africa.