A 25-year-old male had Fanconi's anemia characterized by small stature, the onset of pancytopenia in the first decade of life, a high spontaneous breakage rate of the chromosomes, and the development of acute myeloblastic leukemia. In the preleukemic phase, marrow erythroblasts were multinucleated, and had duplicated nuclear and cytoplasmic membranes with frequent nuclear pockets and cytoplasmic vacuoles, respectively. All neutrophilic and eosinophilic granulocytes had severe quantitative and qualitative defects of granulogenesis; autophagy and nuclear pockets were also observed in the majority of granulocytic cells. Platelets had decreased granulation and extremely dilated canaliculi. Decreased titration scores with anti-I and anti-i were observed with the patient's erythrocytes and those of his clinically normal mother. The unusual morphologic and serologic findings in this patient appear to have resulted from a membrane abnormality affecting the cells of several hematopoietic lines and their organelles.