The discriminant of an
involution of the first kind on a finite-dimensional division algebra over a
field with a Henselian valuation of residue characteristic different from 2
is computed in terms of residue information. We also describe the set of
discriminants of involutions on such division algebras. In the case where the residue
involution is the identity, a stable decomposition of the division algebra into
the tensor product of a semi-ramified and a totally ramified subalgebra is
obtained.