The preliminary results of hydroacoustic investigations conducted aboard the Polish vessel "Profesor Siedlecki” /8.XII.1983 - 8.I.1984/ are presented. In the first leg of the cruise /8-20.XII.1983/ the area between Joinville I., South Orkney Is., Elephant I. was covered. The second leg, named the Second International BIOMASS Experiment, covered the area of the Drake Passage and Bransfield Strait. It was found that total krill stock was much lower than during the First International BIOMASS Experiment /1981/, expecially in the Bransfield Strait. Great concentrations of krill were observed only north and south west and south of Elephant I. and north of King George I.