Inter- and intra-annual variability of commercial krill trawling positions for the 1980/81 to 1999/2000 seasons in the area to the north of South Shetland Islands were analyzed in relation to biological and environmental factors. Commercial fishing perations concentrated on the outer shelf in the early 1980’s, along the shelf slope in the mid- to late 1980’s, and were highly variable, from the shelf across to the outer shelf in the early to late 1990’s. Intra-annual variation of trawling positions showed a general pattern starting from the outer shelf, and proceeded towards the shelf later in the season. Trawling positions seemed to be primarily governed by the distribution of larger mature krill, especially at the beginning of the operation each season. In summer, biological factors that affect product quality such as salp abundance and the proportion of green krill , also seemed to have an increasing effect on trawling positions.. Ice conditions for the recent fishing period were also demonstrated to have an effect.