The affine Toda field theories based on the non-simply-laced Lie algeb
ras are discussed. By rewriting the S-matrix formulae found by Delius
et al., a universal form for the coupling-constant dependence of these
models is obtained, and related to various general properties of the
classical couplings. This is illustrated via the S-matrix associated w
ith the dual pair of algebras f4(1) and e6(2).