Abstract: The present invention relates to a method of regulating or adjusting the transmission power when transmitting signals between a mobile station and a base station in a digital mobile telephony system. The output power is regulated to maintain the transmission power at an optimum level to prevent unnecessary disturbance of neighboring channels transmitting information on the same frequency and to insure that the transmitted information is interpreted properly in the receiver. The measured values of signal strength and signal-transmission quality are collected, and their mean values are calculated. An anticipated value of signal strength and transmission quality is then calculated at a next time-point provided that the transmission power is maintained unchanged in relation to the transmission power at the present or instant time period (t.sub.0). The transmission power at the next time period (t.sub.1) is regulated on the basis of these anticipated signal strength and quality values.