Syst-Eur is a multicentre placebo-controlled outcome trial, designed by the European Working Party on High Blood Pressure in the Elderly (EWPHE), to investigate the effect of antihypertensive treatment on the incidence of stroke in elderly patients with isolated systolic hypertension (ISH). Eligible patients must be at least 60 years old and have a systolic blood pressure averaging 160-219 mmHg with a diastolic blood pressure less than 95 mmHg. The present paper in an interim report on the first 316 patients randomized into this trial. The placebo (N = 170) and active treatment (N = 146) groups were similar at randomization with respect to age (73 +/- 8 years; mean +/- standard deviation), sitting blood pressure (178 +/- 12/85 +/- 7 mmHg), percentage men (34%) and percentage of patients with cardiovascular complications (29%). After randomization blood pressure fell more (p < 0.001) on active treatment than in the placebo group (19 +/- 20/6 +/- 10 mmHg versus 7 +/- 19/1 +/- 10 mmHg for the sitting blood pressure). This first interim report on the Syst-Eur trial demonstrates that a multinational trial in elderly patients with ISH is feasible and that a significant blood pressure difference between the 2 treatment groups can be achieved and maintained. New centres are being recruited in order to randomize a total of 3,000 patients.