Acute hypergranular promyelocytic leukemia (AML M3) belongs to malignant diseases leading very rapidly to death. Immediate treatment based on early diagnosis may cure one third of patients. The typical finding in peripheral blood of patients is pancytopenia with or without atypical promyelocytes. In published studies only 15-25% patients exhibit leukocyte counts above 10 x 10(9)/l. Five of our ten patients studied had leukocyte count above 10 x 10(9)/l. The difference might be in connection with late and slow diagnosis of AML M3. AML is not taken into consideration during medical examination even if the disease occurs in medical family. Thus we describe clinical signs of AML M3 that could be divided into three main groups: bleeding, infections and anemia. In patients with bleeding or anemia or with infections repeating within a short period or with an infection and concurrent signs of bleeding or anemia the complete blood cell count should be examined immediately. If blood cell count abnormalities are found the patient should be sent immediately to hematology unit for further examination and treatment. Early diagnosis enables to start "differentiation therapy" with all-trans retinoic acid that could be administered as monotherapy only in patients with leukocytes below 5 x 10(9)/l. Early diagnosis of AML M3 might ameliorate the fate of patients, since four of our five patients referred to us with elevated leukocyte counts expired in the first five days.