A 3-D prestack Kirchhoff migration is implemented and successfully applied to a 3-D data set from the Ouachita frontal thrust zone in southeastern Oklahoma. The algorithm uses data decomposition and operates efficiently both in multiprocessor vector and parallel environments. Image time maps are precomputed once for each survey point, regardless of how many times it is a source or receiver, and stored in random access disk files. These files, and the data traces, are read asynchronously during migration. Image time computation is done by two-point ray tracing to avoid interpolation between irregularly spaced rays or points on wavefronts. The same software can be used to depth migrate all input data geometries (stacked sections, common-source or common-receiver, or common-offset or common-midpoint gathers). The output images from the Ouachita field data show structural closure on folded thrust sheets of Wapanucka limestone, and repetition of lithology caused by lateral displacement on the thrusts.