The role of carcinogenic agents in the deveolopment of human cancers is now being defined using a variety of human cells as experi- mental model systems. A workshop on "neoplastic transformation in human cell systems in vitro: mechanisms of carcinogenesis" was held at the Georgetown University Medical Center, Washington, DC, on April 25-26, 1991. The aims of the workshop were to present the state-of-the- art in the transformation of human cells in culture, as well as to provide insight into the molecular and cellular changes involved in the conver- sion of normal cells to a neoplastic state...