Human lung cancer is a complex genetic disease resulting from a series of inherited and somatically occurring defects in a number of critical genes. These genetic events, produced in part by carcinogen exposure, include chromosomal deletion, rearrangement, and mutation, and lead to inactivation or activation of certain target genes. Recent data showed these genes to include both recessive oncogenes such as the retinoblastoma gene and dominantly acting oncogenes such as the myc and ras family members.