A notion of $L^2$-determinant is established generalizing $L^2$-torsion. It is shown that classical regularized determinants of elliptic operators converge to $L^2$-determinants in a tower of coverings. A product formula is proved, which provides an Euler-product expansion to regularized determinants, having generalized $L^2$-determinants as Euler-factors.
1991 Mathematics Subject Classification: 58G26, 58F20.