Magnetic moment and electrical resistivity measurements of the Curie (TC) and Néel (TN) points of Gd-Dy alloys show that the region of spiral structure between TC and TN narrows as Gd is added to Dy and disappears at about 50 at. % Gd. Apparently no spiral structure exists in Gd or Gd-rich alloys. The magnetic moments of Dy-rich alloys show the saturation expected when the magnetization is confined to the hexagonal plane (Jgπ/4), but the moments gradually approach the theoretical Jg as the Gd content increases toward 100%. The spin disorder resistivities are not linear in (g-1)2J(J+1); this suggests a variation in the electronic structure of these alloys. © 1964 The American Institute of Physics.