Abstract: An oncotic pressure measurement cell which comprises a transparent plastic upper sample chamber and a lower metallic reference chamber into which the lower, threaded ends of vertical clamping rods are anchored. The upper chamber has vertical passageways through which the rods are passed. The lower metallic reference chamber is coupled, in use, to an appropriate pressure transducer. An aperture is formed in the top of the reference chamber which communicates with the interior of the reference chamber and is covered with a semi-permeable membraneous disc made of plastic. A nylon washer is placed over the disc to retain it in place thereby producing a semi-permeable barrier between the chambers. After this upper chamber is moved downwardly with the clamping rods passing through the passageways, thumb nuts are screwed onto the upper ends of the rods thereby forcing the upper chamber downwardly and pressing the nylon washer tightly against the semi-permeable disc.