Antarctic krill biomass trends in the South Shetland Island region of Area 48 are presented. Updated time series using the Stochastic Distorted Wave Born Approximation, and a dynamic ?Sv krill delineation model are used to derive krill biomass. This paper provides updated (through summer 2007), acoustic biomass estimates previously presented at the 2006 WG-EMM meeting in Namibia (WG-EMM-06/32). In 2007, biomass in the South Shetland Islands region exceeded 19 million tons. This increase from <500 000 tons in 2006 represents the largest biomass recorded in nearly 20 years and a 50% increase over the peak observed in 2003. Biomass was comprised of 1, 2 and 3+ year old krill, suggesting either a large recruitment event was not captured in surveys conducted in 2006 or 2005, or that advection from elsewhere is responsible for the recent increase.