A study of the amplitudes of wide-angle reflections from the sediment-basement interface of old oceanic crust shows that the uppermost portion of layer 2 is homogeneous on the 0.15--1.00 km scale but not on the 3.0--8.0 km scale. The amplitude versus range patterns of the basement reflections recorded on 30 seismic lines were examined; most patterns are affected by the rough topography of the sediment-basement interface. Three lines have smooth travel time curves and appear to be unaffected by topography. The amplitude patterns of these lines are different from each other; they can be modeled by synthetic seismograms computed from velocity structures which have different thicknesses of a transition zone between the limestone sediments and the basaltic crust. ¿American Geophysical Union 1987