Tracking movements of marine animals for extended periods at sea is very expensive and labor intensive. The only method that shows promise for world-wide tracking in long-term studies is satellite tracking. This technique was tested under operational conditions on basking sharks in the North Atlantic Ocean. These fish feed on plankton near the surface, and the long-term objective is to investigate the foraging and migratory movements in relation to sea surface temperature and plankton distribution patterns. A basking shark equipped with a special UHF radio transmitter was tracked for 17 days off the West Coast of Scotland [UK] using the ARGOS satellite data collection and location system. The shark surfaced during warm sunny weather and its movements were localized. Swimming speed was estimated as 0.106 body lengths/s between locations on successive satellite orbits. Simultaneous IR imagery using the NOAA 7 AVHRR indicated the shark''s movements relative to sea surface temperature variations. This preliminary experiment clearly demonstrates the feasibility of satellite-based monitoring of movements of marine animals using currently available operational satellite systems.