  This Topical Review presents an overview of the recent experimental results
on the quantitative determination of the magnetic exchange parameters in
ultrathin magnetic films and multilayers, grown on different substrates. The
experimental approaches to probe both the symmetric Heisenberg as well as the
antisymmetric Dzyaloshinskii--Moriya exchange interaction in ultrathin magnetic
films and at interfaces are discussed in detail. It is explained how the
experimental spectrum of magnetic excitations can be used to quantify the
strength of these interactions.
