To explore the correlation between the C807T polymorphism of platelet membrane glycoprotein I a (GP I a) gene and aspirin resistance in Chinese people, 200 patients with high-risk of atherosclerosis took aspirin (100 mg/d) for 7 days. Platelet aggregation function was detected using adenosine diphosphate (ADP) and arachidonic acid (AA) before and after the administration of aspirin. Then the subjects were divided into three groups according to the results of platelet aggregation function: an aspirin resistant (AR) group, an aspirin semi-responder (ASR) group and an aspirin-sensitive (AS) group. Platelet GP I a gene 807CT polymorphism was examined by means of polymerase chain reaction-sequence specific primers (PCR-SSP). The results showed that T allelic frequency in AR group and ASR group were higher that of AS group (P<0.005), and the prevalence of genotypes (TT+TC) of these two groups was significantly higher than that in AS group (P<0.05). Platelet GP I a T allele was significantly associated with aspirin resistance as revealed by multiple logistic regression (OR=3.76, 95% CI: 2.87-9.58). The results suggest that inherited platelet GP I a variations may have an important impact on aspirin resistance and the presence of GP I a T allele may be a marker of genetic susceptibility to aspirin resistance.