Hadronic contribution to (g - 2)μ

The recent precise measurement of the muon magnetic anomaly (g-2)μ at BNL opens a window into possible new physics, provided the contribution from hadronic vacuum polarization is well understood. This talk summarizes the development in the evaluation of the leading order hadronic contributions. Significant improvement has been achieved in a series of analyses which is presented historically in three steps: use of τ spectral functions in addition to e+e- cross sections, extended used of perturbative QCD and application of QCD sum rule techniques. The uncertainties, in particular concerning the CVC hypothesis used in step, and global quark-hadron duality employed in steps and are discussed. No new analysis results are given in these proceedings. (author)