The fission cross-section ratios for isotopic targets of 240Pu, 242Pu, and 244Pu relative to 235U are measured for neutron energies from 0.5 to 400 MeV and for 239Pu relative to 235U for energies from 0.85 to 62 MeV. A multiple-plate gas ionization detector was used to measure simultaneously the fission rate for each of the isotopic targets. The neutron energies were determined by the time-of-flight technique on a 20-m flight path at the Weapons Neutron Research white neutron source at the Los Alamos National Laboratory Neutron Science Center. Uncertainties are <4% for energies <50 MeV. This measurement provides the capability to resolve discrepancies among previous measurements for these isotopes over this energy range and are the first measurements for most of these isotopes for energies >30 MeV. The results are compared with previous measurements and to ENDF/B-VI.