Recently developed steel-framed floor systems utilizing long-span metal deck have the potential of providing large column free areas with overall floor thicknesses approximately equal to concrete flat plates while typically imposing less dead load on the structure. The vibration serviceability of such floor systems is investigated in this paper. Two laboratory specimens, a full-scale mockup, and 13 in-situ floors were tested to measure their natural modes and responses to walking excitations. Natural modes were determined using experimental modal analysis techniques or heel-drop test results. Response to walking was determined by measuring the maximum peak acceleration due to individual walkers traversing the floor. The natural frequencies for the laboratory specimens and mockup were in the range of those measured for typical composite framing systems whereas all in-situ floors are high-frequency floors. The measured accelerations due to walking and subjective evaluations indicate that such floors will generally have adequate resistance to vibrations due to walking.