The nonlinear coupling term in the Gross-Pitiaevski equation which describes a Bose-Einstein condensate (BEC) can cause four-wave mixing (4WM) if three BEC wavepackets with momenta k 1, k 2, and k 3 interact. The interaction will produce a fourth wavepacket with momentum k 4 = k 1 + k 2 - k 3. We study this process using numerical models and suggest that experiments are feasible. Conservation of energy and momentum have different consequences for 4WM with massive particles than in the nonlinear optics case because of the different energy-momentum dispersion relations.