[en] The mass-dependence of the theoretical contributions to a charged heavy lepton-anomalous magnetic moment is studied. In particular it is shown that the weak interactions effects in the Weinberg-Salam model become very important and are greater than the hadronic effects for a mass of the heavy lepton >or equal to 5 GeV. In order to illustrate the analysis, the theoretical value of the anomalous magnetic moment of the new charged lepton tau(1.9 GeV) is given. The theoretical implications of an eventual measurement of the anomaly of a charged heavy lepton are also discussed