Macrocystis pyrifera, algae which grow to about 60 m in length, are widely present in the Kerguelen Islands. A satellite program has been initiated to map these species quantitatively and qualitatively as well as to establish a possible correlation between their occurrence and sea- surface temperature. Data from SPOT-1 and NOAA-11 AVHRR were acquired during the 1988 austral summer around the area of "l'ile Noire". SPOT-1 data processing has permitted estimation of the biomass (wet weight) of Macrocystis pyrifera at 1 106 kt, spread over an area of 186.30 km2 in the Morbihan Gulf. Supervised classification shows that 30 % of the vegetal coverage carries 60 % of the total biomass. These clusters of seaweed represent a potential of 13 220 tons of industrial-quality alginates. NOAA-11 data have permitted the location of SPOT-1 imagery on the Kerguelen archipelago. The different thematic maps obtained by processing the remotely-sensed data have permitted assessment of previously acquired biological and physical data. The validation of the remotely-sensed data was carried out through a ground-truthing mission at the time of acquisition.