Abstract: A microvolume 3-way stopcock for use in a blood sampling system. The stopcock includes a stopcock body having a cylindrical-shaped central chamber, an inlet fluid passage extending from the central chamber to a connector, a blood sample fluid passage extending from the central chamber to a connector, and a waste fluid passage extending from the central chamber to a connector. A rotatable flow control member having a T-shaped fluid passage is disposed within the central chamber. The rotatable flow control member provides adjustable fluid communication between the inlet, blood sample, and/or waste fluid passages. The stopcock is configured with a small dead space volume in the range from about 0.02 mL to 0.20 mL. A cannula may be connected to the inlet fluid passage. The combined dead space fluid volume of the stopcock and cannula may range from about 0.03 ml to 0.24 mL.