Stress relaxation and strain rate change tests were carried out in annealed Zr-1pctSn-1pctNb-0.1pctFe alloy at room temperature. The apparent and true activation volumes were determined and the results obtained from different techniques were compared. The stress dependence of activation volume was studied in a wide range of stresses, and an analysis was made in the light of the thermal activation theory. The results suggest that surmounting of the Peierls barrier is the rate-controlling factor in the room-temperature plasticity of the alloy. Dislocation exhaustion rate during initial stress relaxation is higher in the alloy.