AbstractThe fission cross sections for233U,235U,239Pu, and241Pu reported in 1958 have been revised using the very precise, recently published, specific activities 21 405±20 dpm/µg233U, 4798.1±3.3 dpm/mg235U, and 746.19±0.41 dpm/mg238U. Revised ratios of fission cross sections at 2200 m/sec are:233U/235U = 0.9142±0.0012,239Pu/235U = 1.2876±0.0034,239Pu/233U = 1.4084±0.0036, and241Pu/239Pu = 1.3506±0.007. Revised fission cross sections at 2200 m/sec in barns relative toσc(197Au) = 98.7±0.2 are:σf(233U) = 527.4±3.1σf(235U) = 576.9±3.4,σf(239Pu) = 742.8±4.4, andσf(241Pu) = 1003.3±5.2. The errors do not include g-factor errors of±0.2% for233U,±0.155% for235U,±0.285% for239Pu, and±0.7% for241Pu.