We present here the sidewise dispersion calculations for the lepton magnetic moment in Weinberg's type of weak interaction model, in the U-gauge formalism. Unsubtracted sidewise dispersion relations hold, but as for the W and Z boson contributions, our results are different from those obtained by the ξ-limiting procedure. The differences are attributed to the non-commutativity of the dispersion intergration and the ξ→0 limit.