  We present a relatively simple argument showing that the H-dyon states
required by S-duality of the heterotic string on $T^6$ are present provided
that the BPS dyons required by S-duality of N=4 supersymmetric Yang-Mills
theory are present. We also conjecture and provide evidence that H-dyons at
singularities where the nonperturbative gauge symmetry is completely broken are
actually BPS dyons.
