  The exact factorisable quantum S-matrices are known for simply laced as well
as non-simply laced affine Toda field theories. Non-simply laced theories are
obtained from the affine Toda theories based on simply laced algebras by
folding the corresponding Dynkin diagrams. The same process, called classical
`reduction', provides solutions of a non-simply laced theory from the classical
solutions with special symmetries of the parent simply laced theory. In the
present note we shall elevate the idea of folding and classical reduction to
the quantum level. To support our views we have made some interesting
observations for S-matrices of non-simply laced theories and give prescription
for obtaining them through the folding of simply laced ones.
