The leading-order hadronic contribution to the muon magnetic anomaly aμ≡(gμ−2)/2aμ≡(gμ−2)/2, calculated using a dispersion integral of e+e−e+e− annihilation data and τ decay data, is briefly reviewed. This contribution has the largest uncertainty to the predicted value of aμaμ, which differs from the experimental value by ∼ 3.6 (2.4) standard deviations for the e+e−e+e− (τ) based analysis. New results since the last workshop and main open issues on the subject are discussed.