Cell to cell associations of immature red cells have been described as septate-like junctions which occur in conjunction with various red cell abnormalities. This study presents evidence that such erythroblast membrane associations are not confined to erythron pathology but are found in erythroblasts of normal, acute granulocytic leukemia, and lymphoma marrows. Observation of these marrows led us to conclude that these erythroblast membrane interactions should not be morphologically or functionally associated with septate junctions since they do not meet the criteria presented in the literature defining the septate junction. Marrow from five normal, healthy male volunteers, five patients with lymphoma, two acute granulocytic leukemias, one erythroleukemia, and one megaloblastic anemia were studied by transmission electron microscopy. In these cases, erythroblasts of the same and/or different stages of maturation were observed in close apposition to each other with ferritin localized between the membranes. We propose that this type of membrane specialization is an erythroblast association which functionally provides for sequestering of ferritin for incorporation into the cell for subsequent hemoglobin production.