This thesis has outlined the development of operations for duodenal ulcer from gastro-enterostomy which sought initially to merely bypass the ulcer, to an increasing physiological approach which progressively sought to reduce gastric secretion whilst minimising operative sequelae. The published results for gastro-enterostomy alone, Polya gastrectomy, truncal vagotomy with gastro-enterostomy and with pyloroplasty and finally for highly selective vagotomy have been critically reviewed. Dissatisfaction with operative mortality and recurrent ulcer as the sole criteria of success led to the development of methods to assess quality of life. The application of computer technology has permitted analysis of quality of life over some 20 years after five principal operations for duodenal ulcer at the Western General Hospital, Edinburgh. Paradoxically partial gastrectomy was associated with a superior quality of life than the more commonly used procedures involving truncal vagotomy. Highly selective vagotomy has been shown to be a safe and effective operation for duodenal ulcer which modifies the diathesis so that recurrent ulcer is more amenable to medical therapy. The incidence of duodenal ulcer has been shown to be in continuing decline. The treatment of perforated duodenal ulcer by simple closure and H2 receptor antagonists has been shown to have superseded immediate definitive operation for perforated ulcer. Surgical treatment of duodenal ulcer has been shown to be associated with an increased long term mortality predominantly through increased respiratory and circulatory deaths in the first post-operative year. A long term increase in death from malignant disease particularly of bronchus has also been demonstrated.