A gate valve structure having a hollow body with inlet and outlet conduits mounted thereon and opposed seat support members mounted on inner ends of the conduits. The opposed seat support members have seat pockets which are finish machined before insertion into the hollow body. The opposed seat support members are in a predetermined spaced relation to each other and they are welded in such spaced relation to the hollow body from a position within the hollow body. One arrangement includes inlet and outlet conduit sections welded to the hollow body and opposed inner conduit sections having the opposed seat support members thereon with the inner conduit sections welded to the inlet and outlet conduit sections from a position inside the conduits to form a continuation of the outer conduit sections. Another arrangement includes inlet and outlet conduits having seat support members welded and finish machined prior to assembly. These conduits are positioned inside the hollow body with the seat support members in a spaced relation and welded inside the hollow body. Annular grooves in the seat support members adjacent the seat pockets aid in stress relieving. A gate is movably mounted between the seat support members.A method of making a gate valve body includes fabricating and stress relieving a seat support assembly, then machining it to finished dimensions, then inserting the seat support assembly into a hollow body member. Next, the seat support assembly is welded inside the hollow body member. Local stress relieving of final welds in the body can be employed.