The effects of smoking on the treatment of angina has been studied in 10 patients. Each patient underwent 4 randomized 1-week treatments consisting of on and off smoking, and on and off propranolol (360 mg/day). At the end of each treatment a maximal exercise test was performed using 16 praecordial leads. Smoking was associated with a significantly higher heart rate, blood pressure, area and severity of ST-segment depression. This was not abolished by propranolol. Thus, smoking aggrevates the simple haemodynamic variables used to assess myocardial oxygen requirements and the electrocardiographic signs of ischaemia; this is true even after treatment with propranolol.