Compensated pressure regulator for use with fluid under pressure comprising: - a hollow body with axis xx', at least one intake for said fluid under high pressure, at least one outlet for this fluid under low pressure from a downstream expansion chamber, a mobile regulation part which slides in a cylindrical bore of said hollow body, and which, forming a piston on which bear on one side the low pressure and on the other side an expansion spring element (5, 20), is able to stop the intake of the fluid at high pressure; - a part with a generally cylindrical form with two heads connected and separated by a cylindrical portion with a smaller cross-section, and of which the two projections along the axis xx' of the two partial inner and opposing faces (28 1, 28 2) are almost of equal surface area, and these two partial inner faces (28 1, 28 2), a portion of a bore surrounding said part in a seal tight manner and a sealing support integral with this bore delimiting a high-pressure chamber, said part with two heads and this bore being movable in relation to one another, such that: - the intake of the high-pressure fluid emerges laterally into this high-pressure chamber, which fluid transmits to the mobile regulation part loads which cancel each other, and the movement of said mobile regulation part is therefore not modified by variations of the high pressure, - the mobile regulation part stops the intake of the high-pressure fluid and isolates, in a seal tight manner, the high-pressure chamber from the downstream expansion chamber by bearing on the sealing support of the head (12 1) located on the low-pressure side of the downstream expansion chamber when the pressure therein transmits a force greater than the opposing force provided by the spring element (5, 20) on the mobile regulation part, - and reciprocally this mobile regulation part opens the intake for the high-pressure fluid from the high-pressure chamber to the expansion chamber when the low pressure therein transmits a force lower than the opposing force provided by the spring element (5, 20) on the mobile regulation part, characterised in that: - the sealing support is a seal, - the part with a generally cylindrical shape with two heads is fixed in relation of the hollow body and the mobile regulation part (23 2) bears the bore and the seal which slide around the part with a generally cylindrical shape with two heads, said mobile regulation part (23 2) sliding itself into another bore of the hollow body. - a hollow body with axis xx', at least one intake for said fluid under high pressure, at least one outlet for this fluid under low pressure from a downstream expansion chamber, a mobile regulation part which slides in a cylindrical bore of said hollow body, and which, forming a piston on which bear on one side the low pressure and on the other side an expansion spring element (5, 20), is able to stop the intake of the fluid at high pressure; - a part with a generally cylindrical form with two heads connected and separated by a cylindrical portion with a smaller cross-section, and of which the two projections along the axis xx' of the two partial inner and opposing faces (28 1, 28 2) are almost of equal surface area, and these two partial inner faces (28 1, 28 2), a portion of a bore surrounding said part in a seal tight manner and a sealing support integral with this bore delimiting a high-pressure chamber, said part with two heads and this bore being movable in relation to one another, such that: - the intake of the high-pressure fluid emerges laterally into this high-pressure chamber, which fluid transmits to the mobile regulation part loads which cancel each other, and the movement of said mobile regulation part is therefore not modified by variations of the high pressure, - the mobile regulation part stops the intake of the high-pressure fluid and isolates, in a seal tight manner, the high-pressure chamber from the downstream expansion chamber by bearing on the sealing support of the head (12 1) located on the low-pressure side of the downstream expansion chamber when the pressure therein transmits a force greater than the opposing force provided by the spring element (5, 20) on the mobile regulation part, - and reciprocally this mobile regulation part opens the intake for the high-pressure fluid from the high-pressure chamber to the expansion chamber when the low pressure therein transmits a force lower than the opposing force provided by the spring element (5, 20) on the mobile regulation part, - the sealing support is a seal, - the part with a generally cylindrical shape with two heads is fixed in relation of the hollow body and the mobile regulation part (23 2) bears the bore and the seal which slide around the part with a generally cylindrical shape with two heads, said mobile regulation part (23 2) sliding itself into another bore of the hollow body.