The present invention relates to a transmission controlling method in a wireless communications system and a receiver for use in the same system. The invention aims at realizing power control (or transmit rate control) more effective than previous techniques by means of utilizing a certain relationship between an error rate and an evaluation amount relating to the estimation amount. Thus, a certain relationship is defined between the evaluation amount relating to a reception condition and an error rate on the receiver, and on the basis of this certain relationship, transmit power of the transmitter is controlled.