A sampling valve for gases or liquids is described, which is capable of operating at high sample pressures (up to 74 kgf cm^-2) or at high temperatures (up to 300 degrees C). For the high pressure operation a Kel F-Teflon-Molykote composite sealing material has been developed. Typical operating conditions are 62 degrees C and 35 kgf cm^-2. When provided with sealings of commercially available polyimide the same valve can be used at temperatures as high as 300 degrees C and pressures of a few atmospheres. The valve is particularly suitable for studies in gas kinetics, since very small vapour or liquid samples can be injected directly from a reaction system into the gas chromatographic column.