The energy splitting 2S _{1 2} - 2P _{3 2} in hydrogenic sulfur ions was measured by laser resonance spectroscopy to be E=2.89526(26) eV. This leads to a deduced value of the Lamb shift E(LS) = 0.10449(26) eV which is 1.7 experimental standard deviations lower than the theoretical value of Mohr.