The use of peripheral blood stem cells (PBSC) with or without bone marrow (BM) in patients with acute myelogenous leukemia (AML) undergoing autologous transplantation in untreated first relapse (Rel1) or in second remission (CR2) was evaluated in a phase II study. Twenty-three patients with AML in untreated Rel1 (n = 8) and CR2 (n = 15) underwent autologous transplant using PBSC with (n = 19) or without (n = 4) BM. Six patients received busulfan (BU) and cyclophosphamide (CY) and 17 received BU, CY and total body irradiation prior to transplant. The median number of CD34+ cells infused was 4.81 x 10(6)/kg (range 0.04-15). Fifteen of 23 patients received post-transplant interleukin-2 (IL-2) at a median of 43 days (range 11-93) in an attempt to decrease relapses. The median day of recovery of granulocytes to 0.5 x 10(9)/I was 12 (range 8-27) and platelets to 20 x 10(9)/I was 15 (range 8-103). Patients received a median of 4 units (range 0-20) of red blood cells and 29 units (range 4-252) of platelets. The probability of 100 day non-relapse mortality was 0.14. The probabilities of survival and relapse at 2 years were 0.24 and 0.65, respectively. The probabilities of relapse in patients receiving (n = 15) and not receiving (n = 8) interleukin-2 (IL-2) were 0.59 and 0.74, respectively (P = 0.1). Overall, seven of 23 (30%) patients are alive and continuously disease-free at a median of 483 days (range 113-835) post-transplant. These data demonstrate that the infusion of PBSC collected after rhG-CSF corrected engraftment problems previously observed with autologous BM transplants in patients with AML but was associated with a high relapse rate.