  The active galaxy Markarian 421 underwent a substantial outburst in early
2001. Between January and May of that year, the STACEE detector was used to
observe the source in gamma-rays between the energies of 50 and 500 GeV. These
observations represent the lowest energy gamma-ray detection of this outburst
by a ground-based experiment. Here we present results from these observations,
which indicate an average integral gamma-ray flux of (8.0 +/- 0.7 +/-
1.5)x10^-10 1/cm^2/s. above 140 GeV. We also present a light curve for
Markarian 421 as observed by STACEE from March to May, and compare our
temporal, as well as spectral, measurements to those of other experiments.
