Abstract: Let T be an n-dimensional torus acting effectively on a 'nice' 2n-dimensional manifold M, with nonempty set of fixed points and suppose that all the isotropy groups are connected. If the action satisfies another hypothesis (equivariant formality) then the quotient space M/T has the structure of a homology cell complex and is in fact a homology disk. We begin by collecting some general facts about actions of compact Lie groups on manifolds. Then we briefly discuss repre- sentation theory of tori and prove some facts about orbits and fixed-point sets of torus actions. Finally, using the Atiyah-Bredon-Franz-Puppe sequence we give a detailed proof of the fact that the quotient space M/T is a homology disk.