Excitation of large-amplitude Alfven waves in an anisotropic electron-positron plasma is investigated with a two-and-one-half-dimensional (2-1/2-D), electromagnetic particle code. If the plasma distribution is a bi-Maxwellian with T-perpendicular to/T-parallel to > 1, where the subscript symbols denote directions perpendicular and parallel to the ambient magnetic field, Alfven waves with arbitrary polarization are generated. Simulations show that the amplitude of the waves increases both with increasing temperature anisotropy and parallel plasma beta(parallel to). The stabilization of individual wave modes occurs sequentially, from higher values of wave number down to lower ones,in the evolution of the temperature anisotropy instability. Wave-particle scattering by the enhanced waves maintains the initially bi-Maxwellian character throughout the simulation, even as it reduces T-perpendicular to and increases T-parallel to. After saturation of wave magnetic energy a large residual temperature anisotropy still remains and persists through the end of the simulation. (C) 1997 American Institute of Physics.