In this Letter, we report the three-photon absorption of hematoporphyrin IX (HpD-IX) in DMSO solution pumping at 1200 nm with a 25 ps pulse laser-OPG system. The obtained three-photon absorption cross-section in HpD-IX, sigma'(3) = 1.2 x 10(-78) cm(6) s(2) ph(-2), is considerably high. Because HpD-IX is one of the main constituent of Photofrine (R) II, the only approved photodynamic therapy drug by the Food and Drug Association, this result is expected to have an impact in deep bioimaging and photodynamic therapy using currently available photosensitisers. (c) 2005 Elsevier B.V. All rights reserved.