The authors investigated the possible association of -4522C/T variation of adiponectin gene with coronary heart disease (CHD) and type 2 diabetes mellitus (T2DM). Genotyping of SNP -4522C/T in 304 patients with CHD, 389 patients with T2DM, and 405 age and sex-matched healthy control subjects was carried out by means of PCR-RFLP approach. No significant difference in the genotype or allele frequencies was found, either between patients with CHD and control subjects, or between patients with T2DM and control subjects. However, in the subgroup analysis, an association of the T/T genotype and T allele with type 2 diabetes combined with obesity (BMI > or = 25 kg/m(2)) was found (P = 0.014 and P = 0.034, respectively). Also the homeostasis model assessment of insulin resistance (HOMA-IR) in T2DM patients with T/T genotype was significantly higher than that in T2DM patients carrying C allele (P = 0.0069). The authors' findings for the first time demonstrated that SNP -4522 in the adiponectin gene was associated with T2DM that combined with obesity and higher insulin resistance index in patients with T2DM. This indicated that the variation might associate with an increased susceptibility to type 2 diabetic obesity and insulin resistance. But -4522C/T polymorphism did not contribute to the susceptibility of CHD.