The branching ratios of various decay modes of K-meson are discussed on the basis of a universal vector and axial-vector four-fermion interaction. The simplest and most straightforward interpretation of the results leads to the following tentative conclusion: The (squared) coupling constant of the strangeness non-conserving baryon-lepton interactions, such as the Λ 0 → p+ e −+ ν or Σ − → n+ e −+ ν , is smaller than the usual Fermi coupling constant (1.4×10 −49erg ac>s ̇ cm 3) by, at least, one order of magnitude. This is rather consistent with the recent observations on the hyperon decays into leptons. Alternative possibilities which may enable us to avoid this conclusion are also discussed. An example is to expect strong final state interactions in the K 0 → π + + π − decay. Also phenomenological estimates of the decay rates of Λ 0 → p+ e −(μ −) + ν from the experimentally known rates of K → μ+ ν and K → π+e( μ)+ ν decays are made. It is concluded that the computed lower limits of the rates are not in contradiction with the present experimental information.