Platelet free cytosolic calcium (PFCC) was measured in 21 healthy volunteers before and after cigarette smoking or physical exercise. The aim was to investigate whether acute blood pressure changes and increases in circulating levels of catecholamines and vasopressin modify PFCC. PFCC was determined using the Quin-2 method. Following cigarette smoking, significant increases in blood pressure, heart rate, plasma epinephrine (35 ± 18pg/ml before versus 51 ± 31 pg/ml after smoking,P< 0.05, mean ± s.d.) and vasopressin levels (0.8 ± 0.3 pg/ml before and 4.2 ± 4.1 pg/ml after smoking,P< 0.001) were observed. However, despite these acute hormonal and hemodynamic changes, PFCC remained stable at 156 ± 55nmol/l prior to the study and 157 ± 29nmol/l and 156 ± 38nmol/l at 20 and 80min post-smoking, respectively. Acute physical exercise led to an increase in heart rate and systolic blood pressure but to a decrease in diastolic pressure. Moreover, a marked increase in plasma norepinephrine levels was observed after exercise (213 ± 71 pg/ml before versus 747 ± 501 pg/ml after exercise,P± 0.001). Again, PFCC was stable at 185 ± 56nmol/l at baseline versus 188 ± 51 nmol/l at 20min and 155 ± 26 nmol/l at 80min after exercise. These results therefore demonstrate that PFCC is not influenced acutely either by blood pressure increases, or by elevations in circulating catecholamine and vasopressin concentrations.