To provide a user terminal, radio base station apparatus, radio communication system and radio communication method that support increases in the number of users, a user terminal is provided with a reception section that receives a downlink control signal multiplexed into radio resources from the starting OFDM symbol to a predetermined OFDM symbol in a subframe, and a downlink control signal subjected to frequency division multiplexing with a downlink data signal into radio resources after the predetermined OFDM symbol, a retransmission check section that performs a retransmission check on the downlink data signal based on the downlink control signal subjected to frequency division multiplexing to output a retransmission response signal, and a selection section that selects a radio resource of an uplink control channel used in transmission of the retransmission response signal.