  We review the renormalization of the electroweak sector of the standard
model. The derivation also applies to the minimal supersymmetric standard
model. We discuss regularization and the relation between the threshold
corrections and the renormalization group equations. We consider the
corrections to many precision observables, including MW and sin^2 theta^eff. We
show that global fits to the data exclude regions of supersymmetric model
parameter space and lead to lower bounds on superpartner masses.
