We describe the use of difference-frequency generation, by mixing two intense femtosecond pulses in a 5-mm long BBO crystal, to generate high power 2.5 μm pulses with a duration of less than 0.5 ps. The pulses are generated by mixing the output of an amplified CPM laser with an amplified part of a continuum. The generated pulses have an energy of 4 μJ which amounts to a photon-conversion efficiency of 5 percent.