The hadronic contribution to (g-2)μ

The evaluation of the hadronic contribution to the muon magnetic anomaly a. is revisited, taking advantage of new experimental data on e(+)e(-) annihilation into hadrons: SND and CMD-2 for the pi(+)pi(-) channel, and BABAR for multihadron final states. Discrepancies are observed between KLOE and CMD-2/SND data, preventing one from averaging all the e(+)e(-) results. The long-standing disagreement between spectral functions obtained from tau decays and e(+)e(-) annihilation is still present, and not accounted by isospin-breaking corrections, for which new estimates have been presented. The updated Standard Model value for a(mu) based on e(+)e(-) annihilation data is now reaching a precision better than experiment, and it disagrees with the direct measurement from BNL at the 3.3 sigma level, while the tau-based estimate is in much better agreement. The tau/e(+)e(-) discrepancy, best revealed when comparing the measured branching fraction for tau(-) -> pi(-)pi(0)nu(tau) to its prediction from the isospin-breaking-corrected e(+)e(-) spectral function, remains a serious problem to be understood.