  Recent progress concerning regularization of supersymmetric theories is
reviewed. Dimensional reduction is reformulated in a mathematically consistent
way, and an elegant and general method is presented that allows to study the
supersymmetry-invariance of dimensional reduction in an easy manner. This
method is applied to several supersymmetry identities at the one- and two-loop
level, and thus the extent to which dimensional reduction is known to preserve
supersymmetry is significantly enlarged.
