Environmental carcinogens are enzymatically activated to form intermediates that can react with cellular DNA and form DNA adducts. Several kind of carcinogens bind to several sites of DNA. The measurement of WBC DNA adducts is a useful indicator for environmental carcinogen exposure monitoring. The 32P-Postlabeling method is a most popular and very sensitive method for DNA adduct analysis. We can analyze 1 adduct/10(8) nucleotides. In this review, I show some data of DNA adduct analysis for PAH exposure. These results demonstrated that inter-individual variation was very large. There were some confounding factors, such as metabolism or repair variations. I also showed some limitations of DNA adduct analysis. The method of adduct analysis is very complicated with several steps. We need to improve the accuracy. Do the data from WBC explain the target organ, such as the lung or liver? Almost all previous studies have been cross-sectional. We need a large-sized cohort study to evaluate whether adducts are a predictor of cancer. DNA adducts should be an important factor in gene-environment interaction.