Objective:To investigate the association of arginase Ⅰ(ArgⅠ)rs2781 666 G/T genotype with the susceptibility of mod-erate and severe chronic periodontitis(MSP)and coronary heart disease(CHD).Methods:DNA was obtained from buccal swabs of 50 patients with MSP,46 with CHD,42 with MSP and CHD,and 50 matched healthy controls.Genotypes of rs2781 666 G/T was analyzed by PCR-PFLP method.The genotype distribution in the 4 groups was compared.Results:Higher representation of ArgⅠrs2781 666 al-lele T was found in CHD group than that in the healthy control individuals(P <0.01 ),and there was no statistical differences among the other 3 groups.Conclusion:Allele T of ArgⅠrs2781 666 may be associated with CHD susceptibility.