Seasonal changes in the Antarctic krill (Euphausia superba Dana) autoproteolytic activity were followed throughout the year. Using the kinetic formula for the first order reaction, the initial reaction rate (y0), the rate after 5 minutes (y5) and the average reaction rate (yx) after 0, 5, 10, 15 and 20 min of incubation of mixed homogenate at 40° + 0.2°C were determined in each sample. Changes in the krill autoproteolytic activity over the year were found to follow a sinusoid with a maximum during the austral summer (January) and a minimum during the austral winter (July-August). The maximum initial reaction rate was about ten times the minimum initial rate, which is an evidence of a considerable seasonal variation in the krill autoproteolytic activity associated presumably with the krill feeding intensity.