SUMMARY The observstlon that carcinogen exposure Is strongly associated with the probability of developing pulmonary neoplasms hassuggested for many yeal'8that acquired somatic mutations play a kay role In the genesis of these environmentally Induced cancers. With the advent of new techniques In cytogenetics and In the molecular analyels of DNA extracted from lung tumors, It has now become possible to test this hypothesis and to search for candidate genes thet may be targeted by the chronic exposure of these envlronmentallnsulta. Early work In this field, studying lung tumors of different histologic types, appeel'8 to Implicate several distinct chromosomal loci (at chromosomes 3p, 13q, 17p,and othel'8), suggesting that sequential genetic eventa occurduring the Initiation and progression pathways to pUlmonary tumorigenesis. Identifying the candidate gene products and understanding the chronology and stringency of mutational eventa at these loci will be anessential goal to understanding the cellular basis of lung tumors and for developing strategies for the next generation of diagnostic and therapeutic studies. AM REV RESPIR DIS 1990; 142:S44-S47