The ordering of the alloy AgAuZn2 has been studied by means of X-ray diffracto-metry. The specimens were quenched from 600℃ and subsequently annealed at 100℃ for various periods of time. It was shown that in the quenched condition almost all of the Zn atoms were at their appropriate lattice sites, whereas the Ag and Au atoms were comparatively less readily to occupy their right places. A very short period of annealing at 100℃ was sufficient to make all the Zn atoms take their proper positions. The ordering among Ag and Au atoms proceeded as annealing was continued, the positions of Zn atoms being unaffected.The size of antiphase domains deduced depended markedly on the indices of reflections during the early stage of domain growth. The final sizes attained in different directions, however, were practically the same. The ordering of atoms and the growth of domains took place simultaneously. However, the degree of order reached a steady value long before the domains attained the final size.