The effects of neutron irradiation on the tensile properties of oxide dispersion strengthened (ODS) ferritic steels have been investigated. Various ODS steels containing 14-22 wt% Cr and 4.5 wt% Al or no Al were produced by mechanical alloying. In order to investigate their susceptibility to hardening and embrittlement induced by neutron irradiation, the ODS steels were irradiated in JMTR at 290, 400 and 600 °C up to doses of 0.01, 0.3 and 0.75 dpa, respectively. Tensile tests were performed at RT before and after irradiation. Microstructure observations were conducted in TEM. It was found that high-Cr-ODS steels show a significant hardening after irradiation at 290 and 400 °C, while no effect was observed after irradiation at 600 °C. The irradiation hardening, however, is not accompanied by a reduction of total elongation. After irradiation at 400 °C the measured hardening increases with Cr concentration, while it is almost constant versus Cr concentration after irradiation at 290 and 600 °C.