Vagal-cardiac baroreflex functions in young healthy humans (n=6) were investigated in four different conditions; supine rest, seated rest, supine and seated exercise (50 watts) before and after 20-day horizontal bed rest. By selectively stimulating carotid baroreceptors using a neck pressure and suction technique, the primary finding was that the baroreflex sensitivity tuation at which we observed a tendency for an attenuation (0.05<p<0.07) of baroreflex sensitivity. The range of decrease in heart rate during neck suction was diminished (p<0.05) after bed rest, but only during supine rest. In conclusion, an attenuation of carotid vagal baroreflex after inactivity was found to be dependent on posture, and was found only in supine rest. It was also concluded that an exaggerated exercise tachycardia found after bed rest is not due to an attenuation of vagal carotid baroreflex sensitivity in itself.