This paper presents the results from a serological survey developed in Mexico during 1987 in order to estimate the prevalence of anti Bordetella pertussis antibodies. Agglutinins were measured in 25,666 samples taken from children one to 15 years old living throughout the country. In each case survey covered some data about social and demographic variables such as socioeconomic stratum, number of DPT vaccine doses received and urban or rural settlement, among others. Titers greater than = 1.16 and 1.32 were considered positive; analysis is based on percent prevalence and geometric means of the antibody titers. We found a 65 per cent of total seropositivity, with higher prevalences in the northern and central states. Agglutinins response was higher among females subjects than in males. Children living in rural areas and those classified as belonging to lower socioeconomic level showed the lowest seropositivity prevalences.