  We describe heterotic string and M-theory realizations of the Randall-Sundrum
(RS) scenario with $\cx N=2$ and $\cx N=1$ supersymmetry in the bulk.
Supersymmetry can be broken only on the world brane, a scenario that has been
proposed to account for the smallness of the cosmological constant. An
interesting prediction from string duality is the generation of a warp factor
for conventional type II Calabi--Yau 3-fold compactifications. On the other
hand we argue that an assumption that is needed in the RS explanation of the
hierarchy is hard to satisfy in the string theory context.
