University of California, and the Applied Fisheries Laboratory, University of Washington. The findings of Operation Troll, the 17,419 mile cruise of the Taney from February 25 to May 3, 1955, were summarized as follows: 1. Sea water and plankton samples show the existence of widespread low-level activity in the Pacific Ocean. Water activity ranged from 0-570 d/min/liter and plankton from 3-140 d/min/g wet weight. 2. There is some concentration of the activity in the main current streams, such as the North Equatorial Current. The highest activity was off the coast of Luzon sveraging 1390 d/min/liter down to 600 m (April 1, 1955). 3. Analyses of fish indicate no activity approaching the maximum permissible level for foods. The highest activity in tuna fish was 3.5 d/min/g ash, less than 1 percent of the permissible level. 4, Measurements of plankton activity offer a sensitive indication of activity in the ocean. 5. Similar operations would be valuable in assessing the activity from future tests and in gathering valuable data for oceanographic studies. The Division of Blology and Medicine of the U. 8. Atomic Energy Commission requested the Applied Fisheries Laboratory of the University of Washington to conduct surveys of the open sea during 1956 to determine "(a) the levels of introduced radioactivity resulting from the tests in the water, plankton, and fish, and (b) how far the activity extends westward in the North Equatorial current.”