On March 25 and 26, 1974, the Tumor Immunology Program of the National Cancer Institute sponsored a workshop on recent progress in the genetic analysis of antibody structural genes. The intent of the meeting was: 1. To define the genetics of markers currently used. In addition to serological studies of defined V-region aUotype markers, investigators have studied other phenotypes, such as idiotype, the magnitude of response to certain antigens, distinctive crossreactivities elicited by certain antigens, unique isoelectric spectra, and others. It is still not known whether these phenotypes are coded for by V-region structural genes. 2. To accumulate linkage data from a variety of systems. For the variety of phenotypes studied, close linkage to CH-region genes could be demonstrated. Combined data from diverse sources yielded valuable information on the linkage relationship of VH and CH. Furthermore, there are indications that genes of the H-chain loci are arranged in an organized fashion. 3. To exchange information on the use of appropriate strains. Because of the complexities of mouse genetics, further attempts to identify additional V-region markers should focus on those strains of mice for which appropriate congenic partners exist and which have been used to derive established recombinant-inbred lines. Detailed linkage analysis is required for strains known to differ by other V-region phenotypes. Abstracts of papers presented at this workshop are appended. However because of the large amount of data from divergent sources, certain topics have beefi summarized and interpreted, hopefully in a unifying way. Until recently, V-region genetics has centered mainly on studies in the rabbit. The particular advantage offered by this species has been serologically defined VH markers associated with VH sequence differences. In combination with CH markers,