A surgical valve includes a housing with a proximal housing portion and a distal housing portion cooperating to define a gel cavity. A seal material is disposed in the gel cavity and includes a gel having flow characteristics and incompressible characteristics. A distal guide tube is provided to facilitate retrograde insertion of a surgical instrument into the seal material. During assembly, pressure is applied by the housing portions to the seal material in order to form a circumferential seal and to close an instrument channel. Manufacture can be facilitated by use of a mandrel for maintaining the structural elements in axial alignment. Complimentary screw threads disposed between the first and second housing portions can be used to pressurize the gel and thereby create a locking force on an inserted instrument. Detented tabs can be provided to facilitate control of this locking force.