Minimal forearm vascular resistances during maximal postischaemic vasodilation were measured in normotensive subjects with syndrome X, a condition characterized by angina and normal coronary arteries, in which a reduced coronary and systemic vasodilatory capacity has been reported. Age- and sex-matched normals and essential hypertensives constituted the control groups. The syndrome X patients had a significantly higher minimal forearm vascular resistance than the normals, indicating that arteriolar alterations may occur in the normotensive state and therefore cannot be considered solely as a consequence of hypertension