This paper describes a pressure vessel which accommodates optical measurements in liquid samples in the pressure range extending to about 4000 kg/cm2and is designed to be used in conjunction with corrosive or sensitive materials. The sample is enclosed in such a manner as to contact only a Teflon compartment and the window surfaces. Simplicity of design is achieved by forming the high pressure seal on the inside window surfaces, an expedient which also permits the inclusion of more than one sample cell in the pressure vessel.