STK15/Aurora-A is a centrosome-localized serine/threonine kinase that functions primarily in centrosome maturation and mitotic spindle assembly. In a large lung cancer case-control study of 1401 cases and 1397 controls including three ethnic groups, we examined the associations between two non-synonymous SNPs (Phe31Ile and Val57Ile) of the STK15 gene and lung cancer risk. There were statistically significant differences in the distribution of the genotypes (P<0.0001) and haplotypes (P<0.0001) by ethnicity for the Phe31Ile, but not the Val57Ile variant. Caucasians with the homozygous variant Phe31Ile genotype (Ile/Ile) were at a significantly reduced risk for lung cancer [odds ratio (OR)=0.63, 95% confidence interval (CI)=0.41-0.96]. The variant allele of Val57Ile was not associated with lung cancer risk overall. However, men with the homozygous variant genotype (Ile/Ile) had a reduced lung cancer risk as compared with men with the wild-type genotype (Val/Val) (OR=0.42, 95% CI=0.19-0.94). When we performed joint analysis of these two polymorphisms, compared with the reference group (TT+GG, 40.99% of controls), homozygous Ile31 allele/wild-type Val57 allele (AA+GG) carriers (5.45% of controls) exhibited a reduced lung cancer risk (OR=0.78, 95% CI=0.63-0.97). This is the first epidemiological study to report significant associations between STK15 polymorphisms and lung cancer risk.