Hemopoietic islets, associations of stromal (macrophages, fibroblasts) and blood (including stem) cells, are structural and functional units of the bone marrow. We studied cellular and molecular processes developing following short-term (1 h) contact of hemopoietic islets with ferromagnetic nanoparticles in a multicellular system of the bone marrow in vitro. It was established that nanodispersions of magnetite (Fe(3)O(4), mean particle diameter 18 nm) and iron coated with carbon (Fe(C), particle diameter 5-10 nm) in a dose of 3 mg/liter had a minor effect on processes of necrotic and apoptotic cell death. Nanodispersion of carbon-coated iron (Fe(C)) most mildly stimulated oxidizing processes recorded by intracellular levels of reactive oxygen species. These nanoparticles, in contrast to magnetite, did not reduce the amount of hemopoietic islets in the bone marrow cell suspension.