The influence of bone marrow recovery on the clinical and radiographic course of invasive pulmonary aspergillosis in patients with acute leukemia has not been well characterized. We studied 26 patients with acute leukemia and invasive pulmonary aspergillosis, comparing those who recovered from chemotherapy-induced granulocytopenia (Group 1, 15 patients) with those who did not (Group 2, 11 patients). Radiographic evidence of pulmonary cavitation was not seen in any Group 2 patient, but developed in 11 of 15 (73%) Group 1 patients (p less than 0.005). In these patients, cavitation always occurred after marrow recovery, an average of 2.0 days (range: 0 to 6 days) after the granulocyte count exceeded 500/mm3. Eight patients in Group 1 and 2 in Group 2 experienced a total of 38 episodes of hemoptysis. Four of the 26 patients, all in Group 1, developed massive hemoptysis (greater than 150 ml of blood per episode), leading to 1 death. In 3 of these 4 patients, cavitation preceded the episode of massive hemoptysis. At the time of massive bleeding, the granulocyte count was greater than 500/mm3, the platelet count greater than 38,000/mm3, and the other coagulation parameters were normal in all 4 patients. Our findings demonstrate that in patients with acute leukemia undergoing chemotherapy, bone marrow recovery markedly influences the clinical and radiographic course of invasive pulmonary aspergillosis. Development of a granulocyte count greater than 500/mm3 is associated with pulmonary cavitation, and on occasion with massive hemoptysis.