Irradiation-induced disordering of bulk Ni3Al under 6 MeV Ni2+ irradiation is studied at room temperature. A self-consistent long-range-order quantification method for ion-irradiated intermetallics is presented using cross-sectional sample preparation and conventional transmission electron microscopy in selected area diffraction depth profiling mode. This method, which does not require the full assessment of dynamic diffraction image simulation information, is unique to precisely measure long-range-order as a function of depth or dose for a single total fluence. The disordering efficiency constant epsilon is estimated in the range 10.0 +/- 0.7/dpa for a total fluence of 10(14) cm(-2). (C) 2000 American Institute of Physics. [S0003-6951(00)03543-9].