Abstract: The inventive method for processing an RR series comprises a plurality of (RR) samples representing time intervals (dti) between two successive heart beats or the inverse (1/dti) of said time intervals consists in selecting (N) (RRi) samples in a main time window having a predetermined length (n), in cutting said main window into (m) subwindows (Fj), in calculating an intermediate parameter (A1) for each subwindow (Fj) on the basis of the (RRi) samples contained in the subwindow (Fj) and in calculating a final parameter as a function of the intermediate parameters (Aj).The invention is used for analysing a cardiac rhythm variability, in particular for assessing a patient's pain or stress.