The structures of metal-thiolate clusters in Zn-7-MT, Cd-7-MT, Cu-12-MT, Ag-12-MT, and Ag-17-MT from rabbit liver have been investigated by sulfur K-edge X-ray absorption spectroscopy (XAS). In addition to providing metal-cysteinyl sulfur bond lengths, the sulfur K-edge EXAFS data provide the first direct evidence for mixtures of bridging and terminal sulfurs in Cu-MT and Ag-MT. The Zn-S and Cd-S bond lengths for tetrahedrally coordinated Zn-4(SPh)(10)(2-) and Cd-4(SPh)(10)(2-) compound obtained from sulfur K-edge EXAFS data are 2.35 +/- 0.03 and 2.52 +/- 0.02 Angstrom, respectively. Zn-S and Cd-S bond distances of 2.34 +/- 0.03 Angstrom for Zn-7-MT and 2.54 +/- 0.02 Angstrom for Cd-7-MT, respectively, calculated from sulfur K-edge EXAFS measurements, are consistent with the previously reported results from metal K-edge EXAFS data.