Objective To determine the prevalance of enhanced signal transduction in immortalized B lymphoblasts from normotensive subjects and patients with essential hypertension, Methods We established Epstein-Barr virus-immortalized lymphoblast cell lines from 26 normotensive and 37 hypertensive subjects. Subsequently, we quantified rises in the cytosolic free Ca2+ concentration, [Ca2+](i), evoked by 0.1 mu mol/l platelet-activating factor (PAF) in Fura-2-loaded cells, Results PAF-induced [Ca2+](i) rises were independent of donor age in cells from normotensive and hypertensive subjects. Baseline values of [Ca2+](i) were not significantly different in the two groups, Using the mean + 2SD of the PAF-evoked rises in [Ca2+](i) above basal (110 nmol/l) as the upper normal value, we estimate that enhanced [Ca2+](i) rises are distinctly more prevalent in hypertensive subjects (27%) than they are in normotensive subjects (4%). Similarly, upon definition of normal values by the 99% confidence interval (75 nmol/l), 19% of cells from normotensive versus 43% from hypertensive subjects display enhanced intracellular signaling. Conclusion Enhanced intracellular signal transduction could be the primary defect in approximately one-third of the overall population with essential hypertension.