  We make a first calculation of eigenfrequencies of radial pulsations of
neutron stars with quark cores in a general relativistic formalism given by
Chandrasekhar. The equations of state (EOS) used to estimate such
eigenfrequencies have been derived by taking proper care of the hadron-quark
phase transition. The hadronic EOS's have been obtained in the framework of the
Brueckner-Hartree-Fock and relativistic mean field theories, whereas the quark
EOS has been derived within the MIT bag model. We find that the periods of
oscillations of neutron stars with a quark core show a kink, which is
associated with the presence of a mixed phase region. Also, oscillation periods
show significant differences between ordinary neutron stars and neutron stars
with dynamical quark phases.
