Measurements of oceanic isoprene were performed during the ASTRA-OMZ (Air–Sea interaction of TRAce elements in Oxygen Minimum Zones) cruise in the eastern Pacific Ocean. The ASTRA-OMZ cruise took place in October 2015 on board the R/V Sonne II from Guayaquil, Ecuador, to Antofagasta, Chile. Up to seven samples (50mL) from 5 to 150m depth for each depth profile were taken bubble-free from a 24L Niskin bottle rosette equipped with a CTD. The water samples were, if necessary, stored in the fridge and analyzed on board, within 1 h of collection.