In the Samaritá area of Säo Vicente city, Säo Paulo State, Brazil, a chemical industry discarded for several years, with no environmental protection, a mixture of residues containing 55 to 85 per cent of hexachlorobenzene (HCB) and others in smaller quantities. In order to evaluate the impact of these residues on the health of the local population, blood serum samples taken from 234 people dwelling at several quarters of this area for over two years were analyzed, divided into 6 sectors: A- Quarentenário and neighborhood of the industrial wastes dump at 67 km; B- Jardim Rio Branco; C- Parque das Bandeiras; D- Gleba II; E- Vila Samaritá; F- Vila Ema, Vila Iolanda, Vila Mathias. Ten blood samples from residents of an area considered no exposed from Itanhaém city were collected to provide baseline information and HCB was not found in any of the samples. HCB residues were analysed by gas chromatography with an electron capture detector, with a determination limit of 0,02 ug/dL. The mean of HCB in blood serum for the inhabitants of the affected area presented significant differences (p<0,001) between sector A (0,41 ug/dL) and all the others sectors; B (0,04ug/dL); C (0,04UG/Dl); d(0,03 ug/dL); E (0,04 ug/dL). Although it has not yet been possible to correlate such findings with the presence of diseases among the area inhabitants, this study indicates that the HCB residues are a health risk, as they not only contaminate the environment, but are also present at the biota, including humans