The pUrpOSE! of this conference was not to define the two areas that are being bound, which might be a well nigh impossible proposition. Rather, its focus was to concentrate on the mechanistic similarities between promotion and progression. Are the areas involved within the boundaries a continuum? Are these two simultaneous processes? Or are some of the affected cells in the stage of promotion when at the same time others have undergone irreversi­ ble changes tha. t position them in the stage of progression? Or are these two stages the same thing, but called by different names? To explore such concepts we assembled investigators with various back­ grounds and asked them to specifically address these and other questions about "The Boundaries", within the context of the session to which they con­ tributed. The conference lasted two and a half days, from Wednesday to Friday. There were at least four speakers per session with morning and after­ noon sessions each day, except on Friday when the meeting ended at noon. The first day, each speaker had 25 minutes to present a position, followed by five minutes of discussion. At the end of the session there were 40 or 50 minutes of exchange on all the issues examined. For the remaining days, there were 25 minutes of presentation and 15 minutes of discussion.

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Introduction: Is There a Boundary between Promotion and Progression; O.Sudilovsky. The Boundaries between Promotion and Progression in Different Tissues: Characterization of the Stage of Progression in Hepatocarcinogenesis in the Rat; H.C. Pitot. Development and Boundaries between Promotion and Progression: Progression in Teratocarcinomas; G.B> Pierce, et al. Transgenic Mice and the Boundaries between Promotion and Progression: Tumor Progression in Transgenic Mice COntaining the Bovine Papilloma Virus Genome; P.M. Howley. Oncogenes, Supressor Genes and the Boundaries between Promotion and Progression: Differential Gene Expression during Tumor Promotion and Progression in the Mouse Skin Model; G.T. Bowden, et al. Genetic Instability and the Boundaries between Promotion and Progression: Genetic Instability and Tumor Development; P.C. Nowell. At Which Point in Time Does Genetic Instability Occur in the Natural History of Cancer? Tumor Heterogeneity and Intrinsically Chemoresistant Subpopulations in Frshly Resected Human Malignant Gliomas; J.R. Shapiro, et al. The Boundaries between Promotion and Progression in Humans: The Human Melanocyte System as a Model for Studies on Tumor Progression; I. Valyi-Nagy, et al. 22 additional articles. Index.