  We present the analysis of the circular polarization, due to Zeeman
splitting, of the water masers around a sample of late-type stars to determine
the magnetic fields in their circumstellar envelopes. The magnetic field
strengths in the water maser regions around the Mira variable stars U Ori and U
Her are shown to be several Gauss while those of the supergiants S Per, NML Cyg
and VY CMa are several hundred mG. We also show that large scale magnetic
fields permeate the CSE of an evolved star; the polarization of the water
masers around VX Sgr reveals a dipole field structure. We shortly discuss the
coupling of the magnetic field with the stellar outflow, as such fields could
possibly be the cause of distinctly aspherical mass-loss and the resulting
aspherical planetary nebulae.
