The frequency of chromosome aberrations was studied in peripheral blood lymphocytes of 29 workers occupationally exposed to a mixture of pesticides and in 14 age- and sex-matched healthy controls. There was a significant increase in chromosome aberrations in sprayers when compared to unexposed persons (2.39% compared to 0.54%). No positive correlation between the frequency of chromosome aberrations and the duration of exposure was observed. No significant difference between smokers and non-smokers was found.