The anisotropy and magnetostriction of single crystals of several ferromagnetic materials have been determined experimentally. The materials include the metals iron and nickel, binary alloys of nickel iron, silicon iron, aluminum iron, cobalt nickel, and cobalt iron, ternary alloys of molybdenum nickel iron, nickel cobalt iron, and molybdenum aluminum iron, and magnetite. The effect of the order‐disorder reaction on these properties was measured for several of the alloys.The present data for the nickel iron and silicon iron systems agree well with recently published values. Ordering generally raises the magnetostriction and lowers the anisotropy of the aluminum iron alloys near the Fe3Al composition. The first anisotropy constant,K1, for the cobalt nickel system as derived from torque curves is similar to old data derived from magnetization curves. However,K1for cobalt iron (30, 35, and 45% cobalt) appears to be considerably larger than previously reported. In general, the addition of cobalt to nickel and to iron changes the magnetostriction constants (&lgr;100and &lgr;111) toward large positive values. Thus, &lgr;100increases to 100×10−6for 50% cobalt nickel and to 130×10−6for 45% cobalt iron; &lgr;111increases to 30×10−6for 45% cobalt iron but remains approximately constant for the cobalt nickel alloys.