The European Working Party on High Blood Pressure in the Elderly study (EWPHE) was a placebo-controlled, double-blind, inter-patient assessment of diuretic treatment in hypertensive patients aged 60 years or more. Of the 840 patients included in the study 247 had isolated systolic hypertension (systolic blood pressure greater than or equal to 160 and diastolic blood pressure less than or equal to 95 mmHg). In those (n = 120) randomized to active treatment (diazide-hydrochlorothiazide with triamterene +/- methyldopa) blood pressure after 3 years was, on average, 19/8 mmHg lower than in the placebo group (n = 119) and after 5 years the difference was 9/7 mmHg. Data on mortality and morbidity were insufficient for firm conclusions to be drawn. The data are presented here only to communicate the trends observed and to provide information that may be useful in the design of future trials. The trends observed for cardiac mortality, terminating non-fatal events (including severe heart failure) and combined fatal and non-fatal cardiovascular events follow a similar pattern to that observed in the trial overall, in that active treatment appeared to confer benefit. However, in the case of isolated systolic hypertension none of these differences between active and placebo treatment achieved statistical significance. We conclude that, given the epidemiological data incriminating systolic hypertension as a risk factor and the data presented here, a rigorous assessment of the value of treating isolated systolic hypertension is justified.