The International Subarachnoid Aneurysm Trial (ISAT) was a large multicentre, prospective randomised clinical medical trial, comparing the safety and efficacy of endovascular coil treatment and surgical clipping for the treatment of brain aneurysms. The study began in 1994. The first results were published in "The Lancet" in 2002, and the 10 year data were published again in "The Lancet" in early September 2005. 2,143 study participants were mostly drawn from U.K. hospitals with the rest drawn from North American and European hospitals.