To ensure that a pilot flying JAS 39 Gripen has adequate arterial pressure at the level of the head, whilst exposed to high G-loads in the head-to-foot direction, he is equipped with an anti-G suit and a pressure-breathing system. Also, the pilot performs Anti-G Straining Maneuvers (AGSM). The purpose was to study (i) the G-protective properties of the anti-G suit alone and (ii) in combination with the pressure-breathing system, and (iii) the interaction of pressure breathing and AGSM whilst wearing anti-G suit. Methods. Nine subjects were investigated in five different conditions in which each subject was: (1) Sitting relaxed, without any G-protective garment. (2) Sitting relaxed and wearing anti-G suit. (3) Sitting relaxed, wearing anti-G suit and pressure breathing. (4) Wearing anti-G suit and performing AGSM. (5) Wearing anti-G suit, pressure breathing and performing AGSM. Subjects were investigated at step-wise increasing G-load (0.5 G/step) to a maximum of 9 G. Results. G-tolerance was 3.3±0.5 G in condition (1), 6.6±1.3 G in (2), =! 8.1±1.0 G in (3), =! 8.9±0.2 G in (4) and =! 9.0±0.0 in (5). In the relaxed state pressure applied in the pressure-breathing system was transmitted undistorted to the intrathoracic space (condition (3)). During AGSM, intrathoracic pressure rose to 10-13 kPa, regardless of whether AGSM was performed without (condition (4)) or with (5) pressure breathing. Conclusions. The anti-G suit and the pressure breathing system provide a combined G-protection of =! 4.8 G, whereas the anti- G suit alone provides a G-protection of about 3 G. The Gprotective properties of the anti-G suit and those of pressure breathing appears to be additive, whereas the Gprotection afforded by pressure breathing does not add to that provided by AGSM.