In 3 patients with ANLL, chemotherapy including high or conventional doses of Ara-C had been ineffective. However subsequent treatment with low-dose (LD) Ara-C induced a PR or CR which were sustained with regular LD Ara-C reinduction courses. Survival of the 2 patients with PR was 24 and 8 months respectively. The patient with CR was alive 18 months after a bone marrow graft. In 2/3 cases, the cytogenetic abnormalities initially detected disappeared with treatment. These observations suggest that the cellular mechanism of action of LD Ara-C is different from that of HD Ara-C, but do not favour a differentiating action of LD Ara-C. LD Ara-C can be prescribed as a salvage therapy even after failure of high or conventional doses.