Lead acetate (PbAc) was tested for its effects on the production and release of erythrocytes‐that is, erythropoiesis‐in ICR mice. Dose‐survival data indicate that a dosage of 20 mg PbAc/100 g body weight represents the maximum tolerable treatment level. No differences in survival at the various levels of the salt were observed with regard to sex or age. For erythropoietic effects of PbAc, mice were injected on day 0, and radioiron (59Fe) incorporation percentages were determined at daily intervals through day 8 for both erythrocytes and splenic tissue. Control mice received isotonic saline as the injectate. On day 3, the percentages obtained from Pb Ac‐treated mice showed a decline, reaching their minimum value by day 4. Recovery from erythropoietic suppression appeared to be complete by day 6 or 7; no positive overshoots in59Fe percentages were found following recovery. These trends were typical for both peripheral red blood cells and spleen. Testosterone was administered to mice receiving saline or PbAc on two consecutive days (days —1 and 0). Radioiron uptake percentages for females receiving testosterone and saline showed an abrupt increase on day 4. No accelerative effect due to testosterone was found in recipient moles. For females treated with testosterone and PbAc, the radioiron percentages for erythrocytes and spleen paralleled those for females receiving saline only. Male mice treated with both androgen and PbAc demonstrated59Fe percentages typical of males treated with PbAc alone.