Abstract: A ball valve is disclosed comprising a single piece body with a ball-shaped, two-part valve member therein operable by a rotatable stem formed separately from the valve member, this stem being so formed that it cannot be blown out from the valve by internal pressure in the valve during servicing.The stem extends from the interior to the exterior of the valve through a stem passage providing, adjacent the chamber which houses the valve member, a first plain bearing supporting a portion of the stem for rotation about the stem axis. The stem has an enlarged portion within the valve chamber which is too large to pass the first plain bearing, the enlarged portion having a shoulder adapted for sealing engagement with a seat formed within the valve body around the stem passage.