The relatively frequent loss of heterozygosity at loci on the short arm of chromosome 11 in human lung cancers has suggested the presence of a putative tumor suppressor gene. For location of the gene, a fine deletion map of human chromosome 11 was constructed by analysis of DNAs from 79 lung cancers with 31 sequence-tagged-site markers that dotted chromosome 11 and detected polymorphic changes in nucleotide sequences. The results showed that three regions, 11p12-p15, 11q12, and 11q14-q24, were commonly deleted in a considerable number of cancers, indicating the possible presence of more than one tumor suppressor gene. The range of deletion in the 11p15 region was estimated to be 4.5 megabases. That in the 11q24-q24 region was divided into two portions: one was 3 cM in length, and the other was longer and could not be specified because of lack of appropriate markers. The deletion in the 11q12 region was so short that two markers flanking the region could not be identified by genetic analysis.