Coke-oven workers are exposed to a high concentration of polycyclic aromatic hydrocarbons, which may change the immunologic responses. In this study, we evaluated humoral immunity by measuring serum IgA, IgE, IgG, and tumor necrosis factor-alpha in 251 coke-oven workers and 89 rolling steel workers in Taiwan. Mean values of serum IgE and tumor necrosis factor-alpha levels were 178.8 IU/mL and 8.4 pg/mL in coke-oven workers, respectively, which were significantly higher than in rolling steel workers (102.6 IU/mL and 2.0 pg/mL; P=0.003 and <0.001). In contrast, serum IgA levels were significantly lower in coke-oven workers than in rolling steel workers (mean=264.7 vs 312.0 mg/dL, P<0.001). Our findings suggest that polycyclic aromatic hydrocarbons exposure may alter the immune responses in coke-oven workers.