Positronium formation with ionic targets using a least-squares approach. R.J.Whitehead*, C.J.Noble~ and B.H.Bransden* *Department of Physics, University of Durham, Durham DH1 3LE, U.K.; ~CLRC Daresbury Laboratory, Warrington WA4 4AD, U.K. The least-squares method has been extended to treat the coupled integro-differential equations representing atomic rearrangement collisions in the close-coupling approximation. Work is currently in progress to add pseudostates to the calculation in order to allow for continuum processes.