Neutron-irradiation-induced embrittlement of a 2.25Cr1Mo steel is investigated by means of small punch testing along with scanning electron trucroscopy. There is an apparent irradiation-induced embrittlement effect after the steel is irradiated at about 400 degreesC for 86 days with a neutron dose rate of 1.75 X 10(-8) dpa/s. The embrittlement is mainly nonhardening embrittlement caused by impurity grain boundary segregation. (C) 2004 Elsevier Inc. All rights reserved.