  We derive the T-duality transformations that transform a general d=10
solution of the type-IIA string with one isometry to a solution of the type-IIB
string with one isometry and vice versa. In contrast to other superstring
theories, the T-duality transformations are not related to a non-compact
symmetry of a d=9 supergravity theory. We also discuss S-duality in d=9 and
d=10 and the relationship with eleven-dimensional supergravity theory. We apply
these dualities to generate new solutions of the type IIA and type IIB
superstrings and of eleven-dimensional supergravity.
