Abstract: Shut-down valve intended for use in a subwater/subliquid position, for instance in subsea pipelines for liquid/gas. It is an object to prevent the medium surrounding the valve, to penetrate the pipesystem which is being served by the valve, and at the same time counteract the through-flowing fluid to be released into the surrounding medium when the valve is to undergo maintenance. The valve comprises a valve housing comprising a cylindrical valve chamber (12,13), which is intended for being oriented along the direction of flow F of the liquid/gas, and a radially arranged valve chamber (14), which is closable with a removable bonnet (9), and also a clack-valve body (3) which is movable between a closed position and an open position.