The pulmonary circulatory response and right ventricular haemodynamics were assessed in normal subjects who sustained hand-grip exercise (HG) at 50% of the maximum voluntary contraction (M.V.C.) for 3 minutes. Ten normal subjects, aged 25 to 66 years, who underwent full right catheterization were studied. The following parameters were taken into consideration: heart rate (HR), end diastolic right ventricular pressure (EDRVP) end diastolic right ventricular volume (EDRVV), mean pulmonary arterial pressure (PAP), pulmonary wedge pressure (PWP), total pulmonary resistance (TPR), cardiac output (CO) and right ventricular sistolic work minute index (RVSWMI). These data were obtained by means of a tip-micromanometer connected with an polygraphic recorder and by means of thermodilution cardiac output computer. The statistical significance of the difference between the resting control values and those after isometric exercise was calculated with the Student's paired t test. A comparison of the control data with those obtained after isometric exercise, demonstrate a statistical significant (p less than 0,001) increase of the HR, PAP, PWP, TRP, CO, RVSWMI, a less significant (p less than 0.01) increase RVEDP. Our findings show that the HG causes changes in the pulmonary circulation and the right ventricular function. Our data seem to sustain that the pulmonary circulation respondes differently under isometric stress than it does under isotonic stress. The use of HG can thus be postulated as a useful means of evaluation of the response of the pulmonary circulation and right ventricular function.