The G-protective properties of a new hydrostatic anti-G suit (Libelle(R); L) were compared to those of the anti-G ensemble used in the JAS 39 Gripen aircraft (AGE-39). Methods. Three pilots were studied in a centrifuge using: (1) the L-suit, (2) the AGE-39 in combination with full anti-G straining maneuvers (AGSM) throughout each high-G exposure (Full Maneuver; FM) and (3) the AGE-39 in combination with AGSM during the initial part of each high-G exposure (Reduced Maneuver; RM). G-intensity tolerance was established during exposures to Rapid Onset Rate (ROR) profiles with G-plataeu levels ranging from +6.0 to +9.0 Gz. G-endurance was studied during Simulated Aerial Combat Maneuvers (SACM) consisting of ten cycles of 5.5 to 7.5 G. Results. G-intensity tolerance was 6.3 G (=mean; range: 6.0-7.0 G) in the L-condition and 9.0 G in all subjects in the FM and RM conditions. Thus, during the ROR exposures only the 6 G profile was completed by all subjects in all three conditions. At this G-load both muscle straining (as indicated by electromyographic activity in thigh and abdomen) and heart rate were higher in the L than in the RM condition Mean arterial pressure at eye level was higher in the FM than in the L and RM conditions. Only one subject was able to complete the SACM profile in the L Kondition In the RM Kondition all subjects completed the SACM profile and in the FM condition two subjects completed the SACM. Conelusions. Whether the AGE-39 was used in combination with maximal AGSM throughout the duration of each high-G exposure or with AGSM only during the initial part of the high-G exposure, G-intensity tolerance was 9.0 G. Whilst wearing the L-suit G-tolerance was 6.3 G. Thus, the G-protection afforded by the L-suit is not adequate for use in a 9 G aricraft.