List of Contents.- Regulation of Foamy Virus Gene Expression.- Transactivation of Cellular Genes by Human Retroviruses.- Regulation of Human Immunodeficiency Virus Type 1 Gene Expression by the Transactivator Protein Tat.- HTLV-1 Oncoprotein Tax and Cellular Transcription Factors.- The Human Immunodeficiency Virus Type 1 Rev Protein: A Pivotal Protein in the Viral Life Cycle.- The Human Immunodeficiency Virus Type 1 Vpu Protein: Roles in Virus Release and CD4 Downregulation.- Viral Protein X.- The Pathogenic Role of Human Immunodeficiency Virus Accessory Genes in Transgenic Mice.- The Human Immunodeficiency Virus Type 1 vif Gene: The Road from an Accessory to an Essential Role in Human Immunodeficiency Virus Type 1 Replication.- Nef.- The vpr Regulatory Gene of Human Immunodeficiency Virus.