In the postgenomic era, the accumulation of massive amounts of molecular and genetic data is quickly transforming the landscape of cancer research. A deeper understanding of cancer biology will allow pathologists studying genetically engineered mouse models and spontaneous tumors to ask novel questions and provide useful insights into disease mechanisms. Although tumor suppressor gene loss is known to be an essential step in the pathogenesis of many tumors, the variety of mechanisms that lead to such loss are poorly understood. This article provides an overview of loss of heterozygosity as an important mechanism of tumor suppressor gene loss; it also emphasizes the importance of loss of heterozygosity detection as a tool for tumor suppressor gene discovery. Understanding the applications of the array of molecular techniques currently available in cancer research will enable pathologists to further contribute to the advancement the field.