Adenovirus early 1 (E1) region gene products, including E1A and E1B, are required for transformation of primary cultured rodent cells. In order to investigate in vivo action of the E1 region, we established a line of transgenic mice carrying the oncogenic E1A and E1B genes of human adenovirus type 12 under control of the human angiotensinogen promoter. Histopathological analyses indicated that transgenic mice heritably develop neuroectodermal tumors arising from the pelvic region with varying degrees of incidence. The transgene was expressed in the neuroectodermal tumors as well as in TNT-1 cells, a cell line established from the tumors, where the human angiotensinogen promoter was constitutively active. The high level expression of c-, L-, and N-myc without gene amplification was notable in the original tumors and TNT-1 cells, but not in another tissue examined. The co-expression of the three sets of myc family genes in both the original tumors and the established cell line provided the possibility that the target cells for transformation may belong to a specific cell type that expresses all these oncogenes during development.