Abstract: A valve is disclosed for allowing a sample to be withdrawn from a processing line under sterile conditions. A tip plug is disposed within a bore and is movable between a closed position and an opened position by rotation of a knob. When the tip plug is in the closed position, a sealing land at the tip plug seals a process stream from a sample port, and an annulus disposed about the tip plug provides fluid communication between a flush port and the sample port. A sterilizing fluid is directed between the flush port and the sample port through the annulus for sterilizing the sample port. The valve is opened by moving the tip plug within the bore, whereby the sealing land moves across a sample port orifice defined by the sample port to thereby provide fluid communication between the process stream and the sample port for withdrawal of a sample from the process stream under sterile conditions.