Pulmonary adenoma susceptibility 1 (Pas1) is a major locus affecting inherited predisposition to the development of lung adenocarcinoma in mice, and is mapped to chromosome 6q near the Kras2 gene. However, it is still unclear whether the PAS1 locus on human chromosome 12p11.2-p12.1, the region showing synteny to the mouse Pas1 region, is involved in susceptibility to human lung adenocarcinoma development. Thus, we conducted a case-control study of 100 lung adenocarcinoma cases and 100 controls using 20 highly polymorphic microsatellite markers dispersed in a 13 cM region covering a putative PAS1 locus. The differences in the allele and genotype distributions were observed at several loci, and the difference was at a maximum at the D12S1034 locus (P = 0.034 and P = 0.036, respectively). The differences in the allele and genotype distributions at D12S1034 remained significant in the analysis in which 239 lung adenocarcinoma cases and 63 controls were added to the 100 cases and 100 controls used for the initial screening (P = 0.031 and P = 0.027, respectively). The D12S1034 locus was located 800-1350 kb proximal to the KRAS2 locus, and in the region syntenic to the core Pas1 region of approximately 1.5 Mb in size where a single haplotype is shared by several mouse-inbred strains susceptible to lung adenocarcinoma development. These results indicate that the PAS1 locus is located in the vicinity of D12S1034 and a genetic variation(s) at this locus is involved in susceptibility to human lung adenocarcinoma.