We discuss the infinite-dimensional algebras appearing in integrable p
erturbations of conformally invariant theories, with special emphasis
on the structure of the consequent non-Abelian infinite-dimensional al
gebra generalizing W-infinity to the case of a non-Abelian group. We p
rove that the pure left sector as well as the pure right sector of the
thus-obtained algebra coincides with the conformally invariant case.
The mixed sector is more involved, although the general structure seem
s to be near to being unraveled. We also find some subalgebras that co
rrespond to Kac-Moody algebras. The constraints imposed by the algebra
s are very strong and, in the case of the massive deformation of a non
-Abelian fermionic model, the symmetry alone is enough to fix the two-
and three-point functions of the theory.