Over the past decade, many experiments have measured the nucleon spin
structure functions using polarized deep inelastic scattering, both in the
US and in Europe.
After a brief survey of these efforts, the results from SLAC experiments
E155 and E155x will be presented. This pair of experiments has measured g1
and g2 of the proton and the deuteron with high precision and over a large
kinematic range, providing the best measurements available. In the
discussion of these measurements, special attention will be given to the
radiative corrections, which have a significant impact on the measured
results and also on statistical and on systematic errors.