— Contents.- DNS-haltige onkogene Viren und Tumorgenese.- I. Allgemeine Beschreibung von Polyoma und SV40 Virus.- II. Allgemeine Beschreibung der Papilloma Viren.- III. Adeno SV40 Hybridviren.- IV. Allgemeine Beschreibung der Adenoviren.- V. Allgemeine Beschreibung der Herpesviren.- Ausblick.- Literatur.- RNA Tumor Virus Oncogenesis.- I. Introduction.- II. General Properties of RNA Tumor Viruses.- III. Replication of RNA Tumor Viruses in Host Cells.- IV. Factors Influencing the Neoplastic Transformation of Cells by RNA Tumor Viruses.- V. Involvement of RNA Tumor Viruses in Human Cancer?.- References.- Murine Virus-Leukämien.- I. Einleitung.- II. Pathobiologie der virusinduzierten murinen Leukämien.- III. Infektiosität und Übertragungsweisen muriner Leukämieviren.- IV. Feinstruktur und Bildungsweise der Mäuseleukämie-Viren und ihre Verteilung im leukämischen und präleukämischen Tier.- V. Murine Leukämieviren in vitro.- VI. Die Immunologie virusinduzierter Leukämien der Maus.- VII. Biochemie der murinen Leukämieviren.- Literatur.- Potential Viral Etiology of Human Tumors.- I: General Aspects.- II: Possible Virus-Induced Human Neoplasms.- III.- Summary.- References.- Molecular Mechanisms of Chemical Carcinogenesis.- 1. Introduction.- 2. Nitrosamines.- 3. Cycasin; Aliphatic Hydrazo, Azo and Azoxy Compounds; Triazenes.- 4. Alkylating Agents and Ethionine. Possible Significance of Nucleic Acid Alkylation.- 5. Aromatic Amines and Azo-Dyes.- 6. 4-Nitroquinoline 1-Oxide.- 7. Polycyclic Aromatic Hydrocarbons.- 8. Aflatoxins.- 9. Pyrrolizidine Alkaloids and Safrole.- 10. Conclusions.- Acknowledgements.- References.- Chemische Carcinogene in der menschlichen Umwelt.- 1. Vorbemerkung.- 2. Einleitung.- 3. Umweltcarcinogene.- Literatur.- Pharmacodynamic Mechanism inCarcinogenesis.- I. Introduction.- II. Cell Cancerization as an Unusual Pharmacodynamic Phenomenon.- III. Summation Action in Carcinogenesis.- IV. Experimental Syncarcinogenesis.- V. Anticarcinogenesis.- References.- Cocarcinogens and Cocarcinogenesis.- 1. Exogenous Cocarcinogens.- 2. Endogenous Cocarcinogens.- 3. Cocarcinogenesis as a Tool for the Investigation of the Biological and Biochemical (Molecular) Mechanisms of Carcinogenesis.- 4. Note on Synergistic Processes in Carcinogenesis.- Conclusion.- References.- Chromosomal Alterations and Development of Experimental Tumors.- I. Introduction.- II. Historical Review of Cytogenetic Studies of Tumor Cells.- III. Karyotype in the Early Stages of Tumor Development and Primary Tumors.- IV. Alteration of Stemline Karyotype in the Course of Serial Transplantations.- V. Chromosome Condition and Invasiveness of Tumor Cells.- VI. Change of Stemline Karyotype During in-vitro Cultivation.- VII. Chromosome Change and Gene Action in Tumor Cells.- VIII. Mutation and Selection for Karyotype Alteration in Tumor Stemline Cells.- IX. Aging of Tumor Stemline Cells and Karyotype Alteration.- Acknowledgments.- References.- Namenverzeichnis — Author Index.- Sachverzeichnis — Subject Index.