Measurements of particulate iron concentrations have been carried out on samples from the western Atlantic Ocean and the Caribbean Sea. Water samples were collected in 30-l Niskin bottles; iron analyses were done by atomic absorption spectroscopy. The average of 184 iron determinations on shallow open-ocean water (0-300 m) was 0.177 µg/l; the average of 112 determinations on deep water (500-7535 m) was 0.255 µg/l....