The expression of NK cells activation receptors was assessed by comparative study of two groups of women workers at a chemical reagents factory, located in Zapopan, Jalisco, Mexico. Twenty of them were exposed to environmental toxics identified and quantified by gas chromatography, and 20 women unexposed to toxic substances. The expression of the surface markers CD56+ and CD3+, and of the activation receptors and co-receptors on NK cells was quantified by flow cytometry. To assess the cellular damage produced by chronic exposure to the toxics, the thiobarbituric acid reacting substances (TBARS) generated and the total plasma antioxidizing capacity (TPAC) were quantified in both groups. The exposed women had been exposed at least to 12 volatile toxic compounds, benzene, benz(a)pyrene, ethylbenzene, dimethylbenz(a)anthracene, xylene, toluene, styrene, chloroform, formaldehyde, iodine, chlorine and fluorine. Significant difference between the two groups was in the proportion of CD3 lymphocytes, 72.7+/-10.3% in the unexposed women versus 66.8+/-7.9% in the exposed group (p