The majority of DNA lesions resulting from interactions of carcinogens with DNA are usually either single strand breaks or lesions which are converted to single strand breaks by treatment of DNA with alkaline solutions. A sensitive method of detecting DNA single strand breaks is the alkaline filter elution of DNA. We started to test this method for biomonitoring occupational exposure with sensitive experimental conditions using pH 12.6, where most alkali-labile DNA lesions are converted to single strand breaks. Under our conditions statistically significant differences can be detected between the elution rates of untreated V79 cells and cells treated with [3H]-thymidine 24 h prior to the elution. Statistically significant increases were detected in the elution rates of male smoking automobile mechanics and male smoking painters compared to non-smoking controls. No statistically significant differences were detected in the elution rates of male non-smoking automobile mechanics and male workers with a suspected exposure to halogenated aromatics compared to male controls. No statistically significant differences were observed in the elution rates of female smoking dry-cleaning workers compared to female smoking controls. Our experience showed that the alkaline elution technique can be a valuable tool for monitoring DNA damage in peripheral lymphocytes in man.