An uplink ACK/NACK signaling method and apparatus in carrier aggregation environment are disclosed. The method for performing a HARQ procedure by a user equipment in a wireless communication system includes receiving one or more control channels carrying downlink scheduling information from a base station (BS), wherein each control channel carries information indicating a total number of control channels transmitted from the BS to the UE, and determining whether the total number of control channels transmitted to the UE is identical to the number of control channels received at the UE.