Spin Structure with Lepton Beams

The next several years should see a significant increase in the amount of data. Precise semi-inclusive data is expected from HERMES. CEBAF^(39) has an extensive program of measurements planned at large x and low Q^2. The new CERN proposal COMPASS^(32) will extend the high Q 2 data and provide information on semi-inclusive charm production, that may shed light on the contribution of gluons to the nucleon's spin. RHIC^(30) (via polarized proton-proton collisions) also has great potential to provide direct information on the gluon contribution. In addition an improved theoretical understanding may be forthcoming with further improvements in the most advanced QCD calculations.