The many levels of metal used in aggressive deep submicron process technologies has made fast and accurate capacitance extraction of complicated 3-D geometries of conductors essential, and many novel approaches have been recently developed. In this paper we present an accelerated boundary-element method, like the wellknown FASTCAP program, but instead of using an adaptive fast multipole algorithm we use a numerically generated multiscale basis for constructing a sparse representation of the dense boundaryelement matrix. Results are presented to demonstrate that the multiscale method can be applied to complicated geometries, generates a sparser boundary-element matrix than the adaptive fast multipole method, and provides an inexpensive but effective preconditioner. Examples are used to show that the better sparsification and the effective preconditioner yield a method that can be 25 times faster than FASTCAP while still maintain accuracy in the smallest coupling capacitances.