The invention relates to a device of the type adapted to deliver fluids, notably medicaments, under pressure. The device comprises a container 1 of variable volume in the form or shape of a pouch or flexible receptacle of generally cylindrical shape with longitudinal pleats 2 containing the fluid under pressure to be delivered and equipped with an actuator C permitting to open a valve 15 a , 15 b to enable the delivery of said fluid, the whole being located inside a container 4 capable of resisting to an elevated internal pressure, the internal volume of the latter container comprised between its wall and the container of variable volume being filled with a neutral gas under a pressure sufficient to exert on the container of variable volume a pneumatic constraint sufficient to permit the delivery of the therein contained fluid when the above-said valve permitting said delivery is operated by the aforementioned actuator C.