To investigate the effect of serum leptin level and leptin receptor (Lepr) genetic mutation on chronic bronchitis, we measured the serum leptin levels of 236 patients with chronic bronchitis and 107 healthy controls by ELISA, the genotype distribution of Lepr gene containing Gln223Arg polymorphic sites by the polymerase chain reaction-restriction fragment length polymorphism (RFLP) method, the levels of inflammatory markers in serum, and the concentration of neutrophils.