  Since the discovery of neutron stars with masses around 2 solar masses the
composition of matter in the central part of these massive stars has been
intensively discussed. Within this paper we will (re)investigate the question
of the appearance of hyperons. To that end we will perform an extensive
parameter study within relativistic mean field models. We will show that it is
possible to obtain high mass neutron stars (i) with a substantial amount of
hyperons, (ii) radii of 12-13 km for the canonical mass of 1.4 solar masses,
and (iii) a spinodal instability at the onset of hyperons. The results depend
strongly on the interaction in the hyperon-hyperon channels, on which only very
little information is available from terrestrial experiments up to now.
