An upper bound can be set to the dipole moment of the X-H bond (with X+H− polarity) for symmetrical molecules of XH4 and XH3 type from the experimental values of the g factor and bond length. The following upper bounds have been found to the bond dipole moments: CH4 μ(C+H−<0.902 D, SiH4, μ(Si+H−)<4.21 D, GeH4+ μ(Ge+H−)<3.59 D, NH3 μ (N+H−)<0, PH3 μ (P+H−)<2.74 D. These results enable one to rule out certain published data on the dipole moment of the C-H bond in methane as certainly incorrect. In the case of the ammonia molecule, the possibility of N+H− polarity is ruled out.