The saturation magnetization of a 31.4 at.% Ni&sngbnd;Fe alloy has been measured as a function of hydrostatic pressure between 0 and 26 kbar, and as a function of shock‐wave compression between 2.5 and 112 kbar. From the hydrostatic pressure measurements, a zero‐pressure value of the pressure derivative of the saturation magnetization (∂ln&sgr;s/∂P) = −3.15×10−2kbar−1is found. A marked departure from linearity of &sgr;s(P) is seen at higher pressures. This is considered to be due to the slope of &sgr;s(T) becoming steeper and steeper at the ambient temperature as the Curie temperature is depressed by pressure. The shock‐wave compression experiments yield a value of (∂ ln&sgr;s/∂P) = −2.8×10−2kbar−1in the 15–40 kbar stress range.