Numerous microtine populations show important cyclic fluctuations of densit
y which have aroused many scientific works, mostly since the fifties. Intri
nsic mechanisms (density-dependence, genetic selection) and extrinsic mecha
nisms (predation, interaction with trophic resources) were both involved fo
r building hypotheses. The present paper gives a survey of the different in
vestigations developed in this field and a review of the mechanisms suppose
dly involved in population fluctuations. As a conclusion we try to build a
synthetic diagram showing the place and the role of the various regulating
factors, and their interactions.