One thousand two hundred and three open-heart operations were performed at Papworth Hospital between 1973 and December 1978 with an early (30 day) operative mortality of 5.3% One hundred patients were treated on an emergency basis. This is defined as an operation necessarily performed within 24 hours of referral to a surgeon. The early mortality in this group was 24 (24 per cent) and accounted for one third of the early deaths during the period under review. The main clinical conditions requiring emergency surgery included ischaemic heart disease (36 patients, early mortality 22.2%; critical valve disease (24 patients, 12.5%; bacterial endocarditis (14 patients, 28.5%; acute aortic dissection (11 patients, 36% and complications associated with valve substitutes (11 patients, 36% Almost all the deaths in the ischaemic heart disease group occurred in those undergoing operation for the complications of infarction. Many factors contribute to the higher risk of emergency open-heart surgery. Of these, dysfunction of other organ systems secondary to low cardiac output and the state of the left ventricle are the most important. Earlier referral for operation of patients with critical valve disease should help to reduce mortality. © 1982 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.