In the event of a cardiac arrest during microgravity exposure, external chest compressions (ECCs) which form the main part of basic life support should be carried out while the advanced life support equipment is being deployed. This study was aimed to determine if there was any gender difference in the effectiveness of performing ECCs using a body suspension device to simulate lunar and Martian hypogravity and microgravity.The volunteers performed ECCs during simulated microgravity (using the Evetts-Russomano method): lunar, Martian, and Earth/Control. Each volunteer performed 3 sets of 30 compressions with 6 s rest in between. The volunteers had their increase in heart rate measured and used the Borg scale to rate the intensity of work after each protocol.The mean depth compressions for men during all gravitational simulations were higher than the women, but both sexes performed effective ECCs during the two tested hypogravity states. During simulated microgravity, men performed significantly deeper ECCs (mean +/- SD of 45.07 +/- 4.75 mm) than women (mean +/- SD of 30.37 +/- 4.75 mm). None of the women achieved the required mean depth of ECCs. Though the increase in heart rate was higher in women, no significant difference was seen in the Borg scale scores between genders during or after the performance of ECCs in microgravity.The results suggest both genders can perform effective ECCs during simulated hypogravity. Women, however, cannot perform effective ECCs during microgravity simulation. These findings suggest that there is a gender difference when performing the Evetts-Russomano method.