  In this talk new formulations of the Green--Schwarz heterotic strings in $D$
dimensions that involve commuting spinors, are reviewed. These models are
invariant under $n$--extended, world sheet supersymmetry as well as under
$N=1$, target space supersymmetry where $n\leq D-2$ and $D=3,4,6,10$. The world
sheet supersymmetry replaces $n$ components (and provides a geometrical
meaning) of the $\kappa$--symmetry in the Green--Schwarz approach. The models
in $D=10$ for $n=1,2,8$ are discussed explicitly.
