Coke oven workers are often heavily exposed to polynuclear aromatic hydrocarbons (PAHs); this exposure has been associated with higher cancer rates among these workers. We assessed the exposure of cokery workers in an oil shale processing plant. Personal hygienic monitoring, measurement of urinary 1-hydroxypyrene (1-OHP), and analysis of PAH-DNA adducts in white blood cells (WBCs) were performed. The32P-postlabeling method was used for adduct measurement. The mean adduct value, 1.6 adducts per 108nucleotides, did not differ significantly from the control value(P = 0.098). Smokers had significantly higher adduct levels than non-smoking workers (P = 0.002). 1-OHP levels measured in post-shift samples correlated with DNA adducts found in white blood cells (WBCs). We conclude that hygienic monitoring and measurement of urinary metabolites are essential background exposure data when the biologically effective dose of chemical carcinogens is assessed.