Abstract: The check valve for infusion and transfusion apparatus comprises a hollow cylindrical member of elastic material which has an open end for the inflow of fluid and an opposite closed end. The hollow cylindrical member has a side wall with an incision in a portion thereof which extends into the hollow interior and provides a flow passage in a direction from the hollow interior outwardly of the cylindrical member. The cylindrical member advantageously has a flange at its entrance end which provides a means for mounting and supporting the valve member. The valve member may be disposed between two connected parts of a housing so that the flange is compressed therebetween and held in position. The construction is usable in a valve housing of a flexible line if the housing includes two interconnected parts which are assembled so as to hold the flange portion of the valve member therebetween.