Abstract: A method and apparatus for cementing an oil or gas well casing including a tubular body section for placing in an oil or gas well casing, the tubular body section being connectable at its upper end to a string of drill pipe and at its lower end to a perforating gun, the tubular body section having a hollow interior, a plurality of upper ports, and a plurality of lower ports, a sliding sleeve located inside the tubular body section adapted to permit drilling fluids to be pumped therethrough and out of the lower ports and to slide downwardly in response to pressure applied to the interior of the string of drill pipe when a seal is placed in contact with the sliding sleeve and thereby activate the perforating gun to perforate the casing, close the lower ports, and open the upper ports to permit cement or other fluids to be pumped outwardly through the upper ports.