It has been shown that motion sickness (MS) reduces the capacity of relaxed individuals to withstand increased G-load in the head-to-foot direction, an effect which may be ascribed to a decrease in resting arterial pressure. In operational flying of high-performance aircraft the pilot commonly performs prolonged or repeated straining, during which the exercise pressor-response plays an important role in increasing the arterial pressure. The purpose was to investigate if the MS-induced reduction of arterial pressure might be overridden by. Methods: The exercise pressor-response was studied in 10 healthy subjects during sustained (90 sec) isometric quadriceps femoris contractions before and after a MS provocation. Results: The exercise bout increased (p<0.001) mean arterial pressure (MAP) and heart rate (HR) by 37±20 mmHg and 26±17 beats/min, respectively. MS reduced (p<0.05) MAP both at rest and during isometric exercise by 11-13 mmHg. Likewise, MS reduced HR (p<0.01) at rest and during exercise by 9-12 beats/min. Conclusions: That motion sickness is capable of supressing arterial pressure also in the face of a strong exercise pressor-response suggests that its G-tolerance decreasing effects may prevail also during repeated anti-G straining maneuvers.