  We present a systematic derivation for a general formula for the n-point
coupling constant valid for affine Toda theories related to any simple Lie
algebra {\bf g}. All n-point couplings with $n \geq 4$ are completely
determined in terms of the masses and the three-point couplings. A general
fusing rule, formulated in the root space of the Lie algebra, is derived for
all n-point couplings.
