Though M31 has been the most studied extragalactic source in HI during the last $\sim$35 years, its rotation curve still remains poorly constrained.

Results from a recent deep HI kinematical survey of M31 performed at DRAO are presented. It will be illustrated how complex its interstellar medium is, showing up to five different HI components along many line-of-sights. A new rotation curve is derived and dark matter distribution models are presented.