Bovine hemoglobin microparticles (Hb-MPs) as suitable oxygen carriers are fabricated easily by three key steps: coprecipitation of Hb and CaCO3 to make Hb-CaCO3-microparticles (Hb-CaCO3-MPs), cross-linking by glutaraldehyde (GA) to polymerize the Hb and dissolution of CaCO3 template to obtain pure Hb-MPs. The Hb entrapment efficiency ranged from 8 to 50% corresponding to a hemoglobin quantity per Hb-MP of at least one-third of that in one erythrocyte. The Hb-MPs are spherical, with an average diameter of 3.2 mu m and high oxygen affinity. The methemoglobin level was increased after preparation, but can be reduced to less than 7% with ascorbic acid. Phagocytosis assays showed low immunogenicity of Hb-MPs if the particles were cross-linked with low concentration of GA and treated with sodium borohydride. Magnetite-loaded Hb-MPs circulated up to 4 days after intravenous application.