  The scintillation light yield of liquid argon from nuclear recoils relative
to electronic recoils has been measured as a function of recoil energy from 10
keVr up to 250 keVr. The scintillation efficiency, defined as the ratio of the
nuclear recoil scintillation response to the electronic recoil response, is
0.25 \pm 0.01 + 0.01(correlated) above 20 keVr.
