  We show that five-dimensional anti de-Sitter space remains a solution to
low-energy type IIB supergravity when the leading higher-derivative corrections
to the classical supergravity (which are non-perturbative in the string
coupling) are included. Furthermore, at this order in the low energy expansion
of the IIB theory the graviton two-point and three-point functions in $AdS_5
\times S^5$ are shown not to be renormalized and a precise expression is
obtained for the four-graviton and related S-matrix elements. By invoking
Maldacena's conjectured connection between IIB superstring theory and
supersymmetric Yang-Mills theory corresponding statements are obtained
concerning correlation functions of the energy-momentum tensor and related
operators in the large-N Yang-Mills theory. This leads to interesting
non-perturbative statements and insights into the r\^ole of instantons in the
gauge theory.
