The concept of structured singular value was recently introduced by Doyle as a tool for analysis and synthesis of feedback systems with structured uncertainties. It is a key to the design of control systems under joint robustness and performance specifications and it nicely complements the H? approach to control system design. This note proposes an equivalent definition of the structured singular value, leading to a fast algorithm for its computation. The speedup over previously proposed methods is at least of one order of magnitude. Due to lack of space, proofs are given elsewhere.