[en] Kinetic measurements with pulsed neutrons were performed in fast subcritical assemblies with a plutonium core (5-8.7 kg) and a uranium (9 cm) or copper (2-7 cm) reflector. The apparatus is described and the data are then presented and discussed. The results obtained by the pulsed neutron and by conventional methods are compared. The paper ends with a discussion of some aspects of the signal-to-noise ratio and the performance of the accelerator and electronics system, with a view to improving the accuracy of the method. (author)