Priming-memory generation in response to Escherichia coli beta-D-galactosidase occurs without antibody formation in irradiated spleen-cell-transferred C57BL/6J mice, which are genetic low responders to the enzyme. Erythropoiesis abolishes priming-memory generation, so that recipients immunized a few days after cell transfer and erythropoiesis induction do not mount a secondary antibody response. Priming-memory generation in cell recipients immunized 3 days after erythropoiesis induction was less frequent than in controls, whereas no significant differences were found when antigen was given before erythropoiesis induction or 5 days after it. The mean titre of the mice escapint suppression was similar to that of the control mice, which became primed and mounted memory. The titre distribution in both responder groups were also similar, although no high-titered responders were found in the erythropoietic mice. Thus while erythropoiesis induction affects the frequency of priming-memory generation, it does not affect to the same extent the amount of memory generated in those mice escaping suppression. The same distinction was observed when spleen cells from erythropoietic mice, containing 30 to 40% erythroblasts, were transferred into normal mice. However, induction of erythropoiesis in non-irradiated non-cell=transferred mice did not cause suppression.