We have prepared a novel oxygen carrier composed of Starburst dendrimer 3 hematoporphyrin iron(III) di-1-(3-aminopropyl)imidazole di-succinic acid (SDHAPI). This compound has a molecular weight of similar to 12.7 kD. O-2 and CO binding to SDHAPI was demonstrated by UV-vis spectroscopy. Oxygenated SDHAPI had an estimated auto-oxidation half-life of 24 min. The oxygen stoichiometry (similar to 6 mol of O-2 mol(-1) SDHAPI) and the k(obs(on+off)) of 0.084 s(-1) and k(obs(aff)) of 0.009 s(-1) were estimated with an oxygen electrode. 2005 Society of Chemical Industry.