Non-small-cell lung cancer is the leading cause of cancer death for men and women in the industrialized nations. Identification of regions for genes involved in its pathogenesis has been difficult. Data presented here show three distinct regions identified on chromosome 11p. Two regions on 11p13 distal to the Wilms tumor gene WT1 and on 11p15.5 between the markers HBB and D11S860 are described. The third region on the telomere of 11p15.5 has been previously described and is further delineated in this communication. By high-resolution mapping the size of each of these regions was estimated to be 2-3 megabases. The frequency of somatic loss of genetic information in these regions (57%, 71%, and 45%, respectively) was comparable to that seen in heritable tumors such as Wilms tumor (55%) and retinoblastoma (70%) and suggests their involvement in pathogenesis of non-small-cell lung cancer. Gene dosage analyses revealed duplication of the remaining allele in the majority of cases in the 11p13 and the proximal 11p15.5 region but rarely in the distal 11p15.5 region. In tumors with loss of heterozygosity in all three regions any combination of duplication or simple deletion was observed, suggesting that loss of heterozygosity occurs independently and perhaps at different points in time. These results provide a basis for studies directed at cloning potential tumor-suppressor genes in these regions and for assessing their biological and clinical significance in non-small-cell lung cancer.