The haemodynamic effects of four weeks of daily intensive training on bicycle ergometer were studied in 10 men with essential hypertension of grade II (WHO). Three weeks before training all medication was replaced by placebo. Five days before onset of training all patients underwent a haemodynamic examination using floating catheter and direct brachial arterial pressure at rest and during effort. The same examination was repeated within five days after the completion of the training. Resting measurements did not demonstrate any effect of the training on systemic pressure or central haemodynamics. At the given load, however, a significant decrease for the pressor response occurred, i.e. lowering of systolic, mean and diastolic arterial pressure. Peripheral vascular resistance was not affected. Cardiac output (Fick) decreased insignificantly both at rest and during effort after training. Heart rate decreased significantly only during exercise. The training lowered significantly both tension time index and left ventricular stroke work index. No adverse clinical or haemodynamic effects of short intensive training were detected in hypertensive patients. There was no evidence of changes in pulmonary artery diastolic pressure considered as an indicator of the left ventricular filling pressure. The heart volume remained unchanged after training.