Polyiodides have been transferred intact from acetonitrile solution to the gas phase and analyzed by mass spectrometry. A range of ions were observed, including I-11, I-13, and I-15, which have higher iodine/iodide ratios than any previously characterized ions. Theoretical calculations show that branched structures are strongly favored, a result which is in excellent agreement with with gas phase fragmentation studies (MS/MS) and also previous solid state studies. This study demonstrates the utility of mass spectrometry to provide structural information in the absence of other spectroscopic handles.