Somatic Mutation: Past, Present, and Future. Instability of Immunoglobulin Genes in Cultured Cells. Kinetics and Molecular Model for Somatic Mutation in Immunoglobulin Variable Genes. Regulation, Timing, and Mechanism of Antibody V Gene Somatic Hypermutation: Lessons from the Arsonate System. A Model for the Development of Somatic Variants in Memory B Cells. Clonal Selection and Hypermutation in the Generation of Immunologic Memory. Hypermutation and Memory B Cells: The Role of Germinal Centers. Unequal Distribution of Replacement Mutations in K and Light Chains and Their Associated H Chains: The Group II Antibody Response to Phosphocholine. Characteristics of Selection-Free Mutations and Effects of Subsequent Selection. Somatic Hypermutation in Transgenic Mice. Templated, Targeted Mutation of Mammalian Immunoglobulin Genes. Evaluation of Possible Mutator Mechanisms Active on Mammalian Variable Region Genes. Hypermutation and Other Variation in Retroviruses. Hypermutation During DNA Synthesis In Vitro.