The precipitation of phosphide and the orientation relationship with the austenitic matrix in P-doped 304L stainless steel have been studied in detail using transmission electron microscopy and computer-simulated stereographic projection. The M3P phosphide was identified in aged samples and confirmed by computer simulation of selected area diffraction patterns. The needle-shaped phosphide is randomly distributed in the austenitic matrix, and grows into thin laths on <001>M austenite planes.