Isoprene ozonolysis yields C1 and C4 stabilized Criegee intermediates (sCIs). Oligomers identified from sCIs reacting with hydroperoxides and carboxylic acids. 34 oligomeric hydroperoxides were identified using iodide HR-ToF-CIMS. Reactive uptake onto acidified sulfate aerosol occurred for most gaseous oligomers. Results indicate that gaseous hydroperoxides could undergo multiphase reactions.