Cosmic Microwave Background Anisotropies and the Geometry of the Universe

In this talk, I review some recent work on cosmic microwave background (CMB) anisotropies in an open universe. I emphasize that the observed CMB anisotropies are still consistent with a low value of $\mathrm{\Omega }$, and I address the question of whether future CMB measurements will be able to provide information on the geometry of the Universe.