['To evaluate the impact of the Janus kinase 2 single nucleotide polymorphisms (SNPs) on gastric cancer risk.', 'In this hospital-based, case-control study, the genotypes were identified by polymerase chain reaction-restriction fragment length polymorphism protocols in 661 individuals (359 gastric cancer patients and 302 age and sex matched cancer-free controls).', 'Both the frequency of A allele in rs2230724 and G allele in rs1887427 were more frequent in patients with gastric cancer (P\u200a=\u200a0.013 and 0.001, respectively). Compared with the common genotype, subjects with the (AG+AA) genotypes of rs2230724 and the (AG+GG) genotypes of rs1887427 had a 59% and 98% increased risk of developing gastric cancer, respectively (P\u200a=\u200a0.010, adjusted OR\u200a=\u200a1.59, 95% CI\u200a=\u200a1.12-2.27; P<0.001, adjusted OR\u200a=\u200a1.98, 95% CI\u200a=\u200a1.39-2.81, respectively). Further stratified analysis showed that the association between the risk of gastric cancer and the rare genotypes of rs2230724 were more profound in the subgroups of elder individuals (>56 years), males, nonsmokers and urban subjects, while the association between the risk and the rare genotypes of rs1887427 persisted in subgroups of younger individuals (≤56 years), males, nonsmokers and both of rural and urban subjects.'] Are janus kinase 2 polymorphisms associated with risk in patients with gastric cancer in a Chinese population?