For pt.II see ibid., vol.12, p.443, 1986. The review of fast-neutron inelastic scattering data for the principal even-even actinide nuclei, as undertaken previously for ²³²Th(n,n') and ²³⁸U(n,n') level excitation functions and angular distributions, is here continued for ^240,242,244Pu(n,n') from threshold to 2.5 or 3.5 MeV. Differential and total (angle-integrated) cross sections have been calculated on the basis of proposed collective-band level schemes in the 'standard' (CN+DI) formalism and in the statistical S-matrix formalism of Hofmann, Richert, Tepel and Weidenmuller (the HRTW approach). For consistency throughout, the optical potential and deformation parameters have followed the Bruyeres prescription, except that for ²⁴⁴Pu Nilsson harmonic-oscillator deformation parameters were chosen. Corrections were applied to the compound-nucleus (CN) cross sections to take account of Moldauer level-width fluctuations, extra n'-channel and radiative-capture competition; for ^240,242Pu+n, fission competition was also taken into account and for ^242,244Pu+n, provision for continuum competition was also made. So far as possible, theoretical data were compared with (the sparse and somewhat unreliable) experimental results and with the ENDF/B-V evaluation: for ²⁴⁰Pu(n,n') the only available measured data were level excitation functions to E_n=1.5 MeV for the 2⁺, 4⁺ and 6⁺ states in the ground-state rotational band and for grouped 'composite' vibrational levels; for ²⁴²Pu(n,n') the experimental excitation function and angular distribution data extended to E_n=3.4 MeV for the 2⁺ and 4⁺ rotational states; no data existed for ²⁴⁴Pu(n,n'). The body of calculated cross-section data thus serves as a comprehensive database for the primary rotational and vibrational states in the three principal even-mass fertile Pu isotopes, wherein the HRTW angle-integrated values demonstrate the viability of this as yet underexploited method.