Evidence of polarized $\gamma$-ray emission ($>$ 50 keV) from Gamma-Ray
Bursts (GRBs) has been accumulated in recent years. Measurements have been
reported with levels in the range of 30-80\%, typically with limited
statistical significance. No clear picture has yet emerged with regards to the
polarization properties of GRBs. Taken at face value, the data suggest that
most GRBs have a relatively large level of polarization (typically, $> 50\%$),
which may suggest synchrotron emission associated with an ordered magnetic
field structure within the GRB jet. But these results are far from conclusive.
Here, we review the observations that have been made, concentrating especially
on the instrumental issues and the lessons that might be learned from these
data.
