The fission cross-section ratios of 233U to 235U and 239Pu to 235U were measured over the neutron energy range from 1 keV to 30 MeV at the Lawrence Livermore Laboratory 100-MeV Linac. Ionization fission chambers and the time-of-flight technique were used to take data simultaneously over the entire energy range. This provided accurate determinations of the shape versus neutron energy of the ratios. Two independent methods were used to determine the average value of each ratio in the interval from 1.75 to 4.0 MeV for the purpose of normalization. Over the 1-keV to 30-MeV range, the total uncertainties for the 233U-to-235U data range from 2 to 4%; the 239Pu-to-235U data uncertainties range from 1 to 4%.