  We present a model for supersymmetric Yang-Mills theory in 10+2 dimensions.
Our construction uses a constant null vector, and leads to a consistent set of
field equations and constraints. The model is invariant under generalized
translations and an extra gauge transformation. Ordinary dimensional reduction
to ten dimensions yields the usual supersymmetric Yang-Mills equations, while
dimensional reduction to 2+2 yields supersymmetric Yang-Mills equations in
which the Poincar\'e supersymmetry is reduced by a null vector. We also give
the corresponding formulation in superspace.
