An HPLC method for analysis of blood protein adducts of methyl bromide was developed. With this method, the alkylated amino acid S-methylcysteine can be quantified both in globin and in serum albumin. The determination of these adducts was implemented in a field study on fumigators who use methyl bromide for the control of insects, nematodes and fungi. Sister chromatid exchange (SCE) was determined in the lymphocytes of the fumigators as an additional biomonitoring parameter. Exposure of persons living in the vicinity of fumigated objects to methyl bromide has been repeatedly reported in the past. The new method for determination of blood protein adducts can be applied for evaluation of such environmental exposure.