Genetic analyses have defined the mutational phenotype of human pancreatic cancer. Knowledge of the genes targeted in human cancers has formed the basis for the genetically engineered mutant mouse models (GEMs) of pancreatic neoplasia. These models depict a spectrum of pathological changes characteristic of the progression of human pancreatic exocrine neoplasia. Three articles in this issue herald the pancreatic cancer research communitythe nomenclature used to describe the genetic knock-out and knock-in models used to represent various stages of pancreatic (and liver) carcinogenesis, and progress in the use of those GEMs. Stemming from a meeting convened on December 1, 2004, in Philadelphia, PA, of more than 100 physicians and scientists with expertise and research interests focusing on pancreatic cancer, a uniform consensus system of nomenclature to characterize pancreatic cancer changes was developed. Adozen GEMs were examined, and the convening scientists classified the models based on gross evaluation of tumors; acinar, ductal, endocrine or interstitial compartment affected; tumor architectural characteristics; cytological changes; and interstitial changes. Many of the histopathologic changes observed in the GEM directly parallel human disease. For details, see the articles by Hruban et al. on pages 14 and 95 and the article by Tuveson et al. on page 242 of this issue. Artwork by Jennifer Parsons-Brumbaugh.