Résumé : Lymphocytes from whole blood cultures from 28 subjects occupationally exposed to different mercury compounds and from seven control subjects were studied cytogenetically. Differences between aneuploidy of exposed and nonexposed subjects were found statistically significant for all analysed mercury compounds. No statistically significant difference however (except for ethylmercury exposure) was observed for the frequency of cells with structural chromosome aberrations although all of the observed frequencies in exposed subjects were higher than those of the controls. A significant correlation was found between the blood and urine mercury levels on the one hand and the total amount of cells with chromosomal aberrations and frequencies of cells with other than chromatid type aberrations on the other. © 1976.