We have examined aqueous solutions of polyiodide ions in KI-I2-H2O solutions at different pressures by Raman spectroscopy. The spectra show a peak at 114 cm−1and a shoulder near 155 cm−1due to triiodide and higher polyiodide ions respectively. There is no observable change in the relative intensities of these bands with pressure up to around 1800 bars, suggesting that iodide speciation reactions are not affected by pressure within this range.