1. The potential value of right vagotomy for the relief of breathlessness has been explored in five patients with emphysema. Two patients had symptomatic improvement, two had minor symptomatic improvement, and one was unchanged. 2. Exercise ventilation was not noticeably depressed by unilateral right vagotomy in the two patients investigated fully, but the pattern of breathing was altered. After vagotomy, breathing was deeper, and the rise in the frequency of breathing with exercise was depressed. 3. After right vagotomy the response to rebreathing carbon dioxide also consisted of slower deeper breaths. 4. Right vagotomy sometimes appears to remove an influence preventing slow deep breathing and exacerbating dyspnoea. 5. Results of bilateral pulmonary denervation, attempted in one patient, were complicated by the need for left thoracotomy, which removed any possible beneficial effects.