Fourteen patients with acute myeloid leukemia (AML) were autotransplanted with peripheral blood cells collected during early remission. Seven were autotransplanted in first relapse and seven in first remission. They received a median of 3.3 X 10(8) nucleated cells/kg body weight (BW) and 92 X 10(4) myeloid progenitor cell (CFU-GM) per kg BW. Rapid hemopoietic reconstitution (HR) occurred in all patients with median time to reach normal neutrophil and platelet counts 13 and 18 days post re-infusion respectively. However, in three patients neutrophil counts fell to less than 1.0 x 10(9)/l and in seven patients platelet counts fell to less than 25 x 10(9)/l between 26 and 40 days post-transplant (trough count). In all but two patients who received the lowest CFU-GM dose the counts returned to normal or near normal levels (steady count). There were significant correlations between the CFU-GM dose and the trough and the steady platelet counts (p = 0.04 and 0.01 respectively). Patients receiving more than 50 x 10(4) CFU-GM/kg BW had higher steady neutrophil and platelet counts (p = 0.011 and 0.033 respectively) although some patients receiving greater than 50 x 10(4) CFU-GM/kg still experienced thrombocytopenia during the second month post graft. There was no significant correlation between the nucleated cell dose and HR. The cause of the fall in platelet and neutrophil counts in the second month post graft is not clear but is probably a reflection of a proliferative defect in the recovery phase stem cells in AML.