This study provides evidence that two VH region a group allotypic specificities are synthesized by individual peripheral blood lymphocytes from a2,3 rabbits. After removal of both allotypes from the cell surface with pronase, three types of allotype-bearing cells, a2, a3, and a2,3 were demonstrable after overnight culture in serum-free medium. Frequently, greater than 50% of the cells that contained allotype on the surface resynthesized both allotypes. In culture, reappearance of allotype was first detectable at 4 hr and increased progressively thereafter to a maximum at 18 hr. During regrowth, the relative proportion of cells showing both markers was maintained. The predominance of cells exhibiting only a3 over those displaying only a2 was also maintained. Reappearance of allotype was inhibited by cycloheximide but was manifested when the antibiotic was washed out. Monospecific anti-a2 antibodies could completely suppress the resynthesis of homologous allotype in culture and prevent the regeneration of a2 in double-bearing cells. Likewise, anti-a3 in cultures was usually specifically suppressive for a3 allotype; however, the double producers were only partially depleted.