The level of peripheral blood granulocyte-monocytic precursors (PB CFU-GM) was studied serially in 10 adult patients with acute lymphoblastic leukaemia (ALL) in early complete remission after induction chemotherapy. The patients were distributed into 2 main groups according to the morphological French-American-British classification: ALL2 and ALL3. Collection of circulating stem cells (CSC) by cytapheresis was performed in 7 of these 10 patients with satisfactory results, except in 2 ALL2 patients, both of whom had chromosome translocation, which could have been a contributing factor. It appears, moreover, that even with 2 or 3 inductions courses, the more intensive the chemotherapy regimen in previously non-treated patients, the higher the peak of PB CFU-GM and the better the collection of CSC. The measurement of CFU-GM is certainly a less effective indicator of pluripotent stem cells in blood than in bone marrow, and it is probably necessary, but sufficient, to inject 5 times more CFU-GM than normally injected in marrow transplants to allow prompt and stable engraftment. The feasibility of this new graft technique seems for the moment undeniable, the main problem in ALL is the risk of relapse.