  We demonstrate that all rational models of the N=2 super Virasoro algebra are
unitary. Our arguments are based on three different methods: we determine Zhu's
algebra (for which we give a physically motivated derivation) explicitly for
certain theories, we analyse the modular properties of some of the vacuum
characters, and we use the coset realisation of the algebra in terms of su_2
and two free fermions.
  Some of our arguments generalise to the Kazama-Suzuki models indicating that
all rational N=2 supersymmetric models might be unitary.
