Coulomb energies in S -shell nuclei and hypernuclei

We estimate the Coulomb energy component of the /sup 3/He-/sup 3/H binding energy difference, using the latest elastic electron scattering form factor data, to be 639 +- 19 keV, in agreement with previous estimates. We estimate the Coulomb energy of /sup 4/He to be 757 +- 23 keV. We discuss the Coulomb energy contribution to the ..lambda.. separation energy difference B/sub ..lambda../(/sup 4/He) -B/sub ..lambda../(/sup 4/H).