Out of 75 consecutive elderly AML patients who did not receive anti-leukemic treatment (52 pts) or failed to respond to differentiating agent (23 pts), 6 patients had survivals of 13.2 to 98 months with treatment restricted to supportive care. This cut-point is far longer than the median survival of the 235 elderly patients (3.5 mo.), either untreated (med. survival: 1 mo.) or treated (with treatment ranging from conventional induction to palliative chemotherapy) (4 mo.), admitted to our department within the same period of time. These cases of smoldering AML (4 women, 2 men) were all of AML2 FAB subtype (4 de novo, 2 post MDS) and presented with a significantly better performance status, lower WBC and circulating blast counts, higher platelet counts and with lower bone marrow infiltration than AML cases with more rapid progression. Cytogenetical analysis when available (3 pts) showed normal karyotypes and clonogenic assay performed in 3 of these patients showed a lack of (2 pts) or reduced in vitro leukemic cell growth (1 pt). The identification of specific characteristics of smoldering leukemia in the elderly might be an important development in the understanding of the physiopathology of acute leukemia and a tool for helping decision-making when selecting the time and intensity of cytotoxic treatment in these older patients.