  We study the hadron-quark phase transition in the interior of neutron stars.
The relativistic mean field (RMF) theory is adopted to describe the hadronic
matter phase, while the Nambu-Jona-Lasinio (NJL) model is used for the quark
matter phase. The influence of the hadronic equation of state on the phase
transition and neutron star properties are investigated. We find that a neutron
star possesses a large population of hyperons, but it is not dense enough to
possess a pure quark core. Whether the mixed phase of hadronic and quark matter
exist in the core of neutron stars depends on the RMF parameters used.
