For the continuation of the study undertaken during the Amsterdam Symposium and within the framework of the "Work Group on the Behavior of Hydraulic Machinery under steady oscillatory conditions" the authors have the following objectives: - comparison between the experimental responses of the circuit to a piston machine excitation and the calculated responses by the impedance method; - comparison between the experimental responses of the circuit to a piston machine excitation and the responses to excitation produced by the flow at partial load; - conditions under which a pulsation phenomenon occurs at high loads. The first aim is achieved but yet under restrictive conditions. The second investigation shows that the scale effects of fluctuations versus/test head have the same tendencies as the frequency responses of the circuit but that the occurence of cavitation deeply changes such responses. Finally, the occurence of pulsations at high loads is closely related to the axisymmetric vapor amount in the draft tube and the pulsation frequency also varies with the characteristics of this vapor amount.