Distribution of the standing crop of phytoplankton and primary productivity in the Gerlache and Bransfield straits was studied during February and March 1965 aboard the Argentine Navy Icebreaker GENERAL SAN MARTIN. Relatively high standing-crop values, expressed in chlorophyll a per square meter, were exhibited in the euphotic zone, with ranges of 86-209 mg/m2 in the Gerlache Strait area and 20-209 mg/m2 in the Bransfield Strait area. Primary productivity was also high in both areas, but not commensurate with what might be expected for the standing crop in Gerlache Strait....