CHABLIS was a NERC-AFI funded project, aimed at studying the chemistry of the Antarctic Boundary Layer in greater detail, and for a longer duration, than has previously been attempted. Field measurements were carried out at the British Antarctic Survey station, Halley, at the Clean Air Sector Laboratory (CASLab). Year-round measurements began in February 2004, with a focus on NOy partitioning, air-snow exchange, and a spring-time halogen/ozone depletion intensive. A summer campaign focusing on oxidants ran during January/February 2005, after which CHABLIS fieldwork ended.