  The recent NA48/2 improvement on R_K=Gamma(K->e nu_e)/Gamma(K->mu nu_mu)
emphasizes the role of K_l2 decays in probing the mu-e universality.
Supersymmetric (SUSY) extensions of the Standard Model can exhibit mu-e
non-universal contributions. Their origin is twofold: those deriving from
lepton flavor conserving couplings are subdominant with respect to those
arising from lepton flavor violating (LFV) sources. We show that mu-e
non-universality in K_l2 is quite effective in constraining relevant regions of
SUSY models with LFV (for instance, supergravities with a see-saw mechanism for
neutrino masses). A comparison with analogous bounds coming from tau LFV decays
proves the relevance of the measurement of R_K to probe LFV in SUSY.
