  The kilohertz quasi-periodic oscillations (kHz QPOs) have been found in
neutron star low mass X-ray binaries (NS-LMXBs), which present the millisecond
timing phenomena close to the surface of the compact objects. We briefly
summarize the following contents: (1). The correlations and distributions of
twin kHz QPOs; (2). The relations of high-low frequency QPOs; (3). The QPO
properties of NS Atoll and Z sources; (4). No clear direct correlations between
NS spins and QPOs; (5). The mechanisms of kHz QPOs; (6). The implications of
kHZ QPOs, e.g., NS mass and radius, disk thickness and magnetic field of Atoll
and Z source.
