In a study of psychological adjustment to coronary artery bypass surgery 23 patients who underwent surgery were seen pre-operatively, prior to discharge and one year after surgery. A comparison sample of 19 patients not tested pre-surgically was contacted by postal questionnaire one year post-operatively. An hierarchical grouping analysis carried out on seven outcome variables yielded a two-group solution for the study sample and this was replicated in the comparison sample. Group 1 indicated change for the better and Group 2 change for the worse since surgery. Discriminant function analysis of 23 pre-operative and operative variables for the first sample indicated ability to cope with stressful events and neuroticism were significant predictors of outcome. Patients in the comparison sample did not differ from the study sample in outcome measures, indicating no effect of assessment prior to operation for the study sample.