Polarization and Weak Mixing Angle in High Energy e^pm e^- Collisions

At a linear collider of the next generation the large event rates expected from Bhabha and M\o ller scattering may be used to determine simultaneously sin^2\theta_w and the polarization of both beams with very high accuracy. These measurements can be performed in parallel to the other tasks of the linear collider as a free by-product. A high degree of polarization and a good polar angle coverage of the detectors turn out to be major assets.