Chromium-molybdenum seamless steel tubing in five sizes was welded into butt, T, and lattice joints. The chemical composition and mechanical properties of the various tubing sizes as well as those of the three sizes of welding wire are given. Forty joints were welded and tested to determine their strengths. The weight and time required to fabricate each joint were measured. The results of all these tests are tabulated and conclusions are drawn. It is believed that a close estimate of the strength of any aircraft structure joint can be made by referring to the test results of one or more of the specimens.