Chen F, et al. - Authors preliminarily explored the correlation between serum copper (Cu) and zinc (Zn) levels and oral cancer risk with relatively large-scale samples. A significant correlation of both serum excess and deficient levels of Cu or Zn with oral cancer risk was suggested in this preliminary study, which may provide a new insight on the roles of serum Cu and Zn in oral cancer. Moreover, the aforementioned trace elements and smoking demonstrated multiplicative interactions.