Résumé
We present a long-term spectropolarimetric study of the active M giants EK~Bootis (M5III) and ${\beta}$~Pegasi (M2.5II-III). For each star, the variability of the disk-averaged longitudinal component of the magnetic field (${B_l})$ is shown, along with the behavior of different spectral activity indicators. The possible nature of the secondary component of EK~Boo is discussed. We compare the observed variations in the activity proxies of each of the two giants and discuss possible physical explanations for the structure of their respective magnetic fields. For both objects, observations in linear polarisation are also presented and briefly discussed.