We investigated the clinical and non-clinical factors which influence the waiting time from initial angiography to bypass surgery, by follow-up of a random sample of 141 patients undergoing their first coronary angiography, for whom a decision to revascularize was made in 1991. The period between the date of angiography and the date of surgery, and a variety of clinical patient characteristics, were retrieved from medical notes in mid-1993. Patients were sampled from those investigated in the two Northern Ireland catheterization laboratories in Belfast, both of which were served by one local surgical centre. Of the 141 patients studied, 86 had had surgery at follow-up. The most important predictors of waiting time were: the presence of severe stenosis of the left main-stem coronary artery [relative hazards, 3.4 (1.6-7.3)], the presence of unstable angina at the time of angiography, [relative hazards, 2.2 (0.97-5.0)], age at angiography, [relative hazards, 2.2 (1.1-4.2) for > 65 years vs. < 50 years], having a positive family history of premature coronary artery disease in a first-degree relative, [relative hazards, 1.8 (1.1-2.9)] and smoking habit at angiography, [relative hazards 0.6 (0.3-1.1), for current vs. never/ex-smokers]. More weight appears to be given to maximizing life extension rather than its quality enhancement in determining who gets priority for surgery. The exception to this may be in regard to smokers, and purchasers might find it useful to set targets for secondary prevention activities with respect to such patients.