Organochlorine (OC) pesticides have been extensively used for pest control in agriculture and against malaria vectors in the region of Soconusco, Chiapas, in southern Mexico. Our study aimed to identify whether the inhabitants of four Soconusco communities at different locations (i.e., altitudes) and with different history of use of OC pesticides, have been similarly exposed to residues of these pesticides. In particular, we analyzed the potential relationship between levels of OC pesticides in plasma and the age, gender, and residence of the study population (n = 60). We detected seven pesticides in total (gamma-HCH, beta-HCH, heptachlor, p,p'-DDE, p,p'-DDT, beta-endosulfan, endrin aldehyde). Of these, p,p'-DDE and beta-endosulfan were the most frequently found (in 98% and 38% of the samples, respectively). The low-altitude (60 years) had the highest p,p'-DDE level (56.94 +/- 57.81 mu g/L) of all age groups, while men had higher p,p'-DDE (34.00 +/- 46.76 mu g/L) than women. Our results demonstrate that residents of the Soconusco region are exposed to p,p'-DDE because of high exposure to DDT in the past and current environmental exposure to this DDT-breakdown product.