Antarctic perennial sea-ice processes differ markedly from those that dominate in the Arctic. These processes – surface flooding, formation of snow ice and superimposed ice, and the development of porous gap layers which harbour rich biological communities – control the growth and properties of perennial ice, yet understanding has been hampered by limited observations, particularly of the temporal evolution of the ice. We present an overview of sea-ice observations obtained during three cruises in the summer perennial ice in the Bellingshausen Sea (February–April 2007), Amundsen Sea (January–February 2009) and Weddell Sea (February 2009). These comprise two primary datasets: (1) ice-core data obtained from 16 and 20 floes in the Bellingshuasen and Amundsen Seas, respectively; and (2) ice mass-balance buoys (IMBs) deployed in the Amundsen and Weddell Seas that provide data over almost an entire annual cycle. Ice-core data show a high degree of regional variability in surface ice types. Notably, in the Bellingshausen Sea, several thick multi-year floes had a superimposed ice layer a meter or more thick, much more than previously reported. Gap-layer communities were widespread throughout the region, but manifested in at least two distinct forms suggesting multiple mechanisms of formation. Satellite and buoy ice-drift data suggest that perennial ice in the Amundsen Sea is sustained partly through import of thick ice from the western Bellingshausen, where perennial sea ice tends to be most persistent. However, most ice in 2009 was thinner and < 1 year, partly due to an almost complete removal of ice from the Bellingshausen Sea in the summers of 2007 and 2008. IMB data show a stark contrast between perennial ice evolution in the Amundsen and Weddell Seas. Modest basal growth (~20 cm) was observed in the Weddell Sea due to the thin snow cover. High snow accumulation rates in the Amundsen Sea caused extensive flooding, warm ice and extensive basal and surface melt. These data are compared with results of a one-dimensional thermodynamic/fluid dynamic sea-ice model. Results show that surface ice properties and gap-layer formation are controlled in part by the interplay between flooding, snowmelt and superimposed ice formation. This highlights the need for improved understanding of snow and summer melt processes in the Antarctic for understanding the impact of climate variability on both sea-ice mass balance and biological communities.