Abstract.We show that if X is a cocompact G-CW -complex such that each isotropy subgroup Gσ is L (2) -good over an arbitrary commutative ring k, then X satisfies some fixed-point formula which is an L (2) -analogue of Brown's formula in 1982. Using this result we present a fixed point formula for a cocompact proper G-CW -complex which relates the equivariant L (2) -Euler characteristic of a fixed point CW -complex X s and the Euler characteristic of X/G. As corollaries, we prove Atiyah's theorem in 1976, Akita's formula in 1999 and a result of Chatterji-Mislin in 2009. We also show that if X is a free G-CW -complex such that C * (X) is chain homotopy equivalent to a chain complex of finitely generated projective Zπ 1 (X)-modules of finite length and X satisfies some fixed-point formula over Q or C which is an L (2) -analogue of Brown's formula, then χ(X/G)=χ (2) (X). As an application, we prove that the weak Bass conjecture holds for any finitely presented group G satisfying the following condition: for any finitely dominated CW -complex Y with π 1 (Y )=G, Y satisfies some fixed-point formula over Q or C which is an L (2) -analogue of Brown's formula.