The laser desorption/ionization (LDI) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra of trinuclear CS3Re3Cl12 and Cs3Re3Br12 and dinuclear (Bu4N)(2)[Re2Cl8] are reported. In each case, characteristic fragments due to the loss of halogen atoms give ion signals that can be used to identify the number of rhenium atoms and the identity of ligands bound to the cluster. The ion signals are identified by both m/z values and distinctive isotope patterns. The results presented here illustrate the usefulness of MALDI-TOF mass spectrometry in the characterization of metal atom clusters.