Amorphous Fe40Ni40P12B6was compressed in the diamond anvil cell up to a 250 kbar pressure, and the pressure was measured as a function of position with the ruby fluorescence method. Analysis of the spatial distribution of the pressure indicates that the flow stress &sgr;yof the material varies as &sgr;y= 17 exp(0.004P), with &sgr;yandPexpressed in units of kbar. The increase in the flow stress with pressure corresponds to an activation volume of 0.16 A˚.3The pre‐exponential factor represents the flow stress of the material at zero pressure. Because the material in a diamond cell is subjected to a very extensive plastic flow before the pressure distribution is established, this value is not necessarily identical to the flow stress measured with more conventional methods, involving no or very little prior plastic deformation. The latter methods tend to measure higher values for &sgr;y, indicating that metallic glasses undergo work softening when deformed extensively.