The present invention is designed to flexibly report aperiodic channel state information to a plurality of radio base station apparatuses to be coordinated, even when coordinated multiple-point (CoMP) transmission/reception is performed.A radio communication system includes: a radio base station apparatus that transmits an uplink scheduling grant, which includes a request field that requests reporting of channel state information from a user terminal, and an identification field that identifies a radio base station apparatus to which aperiodic channel state information should be reported, among a plurality of radio base station apparatuses that perform coordinated multiple-point transmission/reception, to the user terminal, via a downlink control channel; and a user terminal that estimates a channel state with respect to a radio base station apparatus that is designated by a combination of the request field and the identification field, and reports the channel state information to the radio base station apparatus via an uplink shared channel.