A model of predator-prey interaction in a chemostat with Holling Type II functional and numerical response functions ofthe Monod or Michaelis-Menten form is considered. It is proved that local asymptotic stability of the coexistence equilibriumimplies that it is globally asymptotically stable. It is also shown that when the coexistence equilibrium exists but is unstable,solutions converge to a unique, orbitally asymptotically stable periodic orbit. Thus the range of the dynamics of the chemostatpredator-prey model is the same as for the analogous classical Rosenzweig-MacArthur predator-prey model with Holling TypeII functional response. An extension that applies to other functional rsponses is also given.