Among 195 patients with variants of acute myelogenous leukemia (AML), a minimum of 11 met our criteria of smouldering AML: patients with less than 30% of blast cells plus promyelocytes in the bone marrow at the time of diagnosis who were observed without specific antileukemic therapy for a period of at least 6 months without entering a fulminant stage of the disease. These patients were older than other patients with AML, they had initially relatively few infections, bled rarely, and did not enter the fullblown clinical picture typical of acute leukemia until the last months of life. For these 11 patients the median survival time was 29 months from the time of diagnosis. Patients with smouldering leukemia shall be observed carefully and not be given specific antileukemic therapy, at least not before they flare into a blast crisis. Transfusions, antibiotics and a small dose of prednisone should be given when necessary.