Abstract: A combination pipe piercing fitting and valve including a housing formed of a weldable plastic and having a valve casing communicating with a branch nipple. In the valve casing a valve stem and a boring tool are disposed for axial movement so as first to pierce a pipe welded to the housing and to then selectively open or close the branch nipple from the pipe. A sleeve for guiding the boring tool is axially and rotationally secured in the valve casing and extends at least past the area where the branch nipple enters the valve casing. This guide sleeve has a valve seat at its bottom end and an opening adjacent the branch nipple. This combination fitting and valve assures high operating reliability without leakage both during piercing of the pipe and during operation as a valve.