Test results are summarized for thermal-shock specimens and mock-ups of ferritic and austenitic steels. In addition, complete test data are reported for a laboratory test program which was undertaken to supplement the full-scale tests. Thermal-shock tests of 6-in. pipe-and-valve assemblies in both 18-8 Cb and 2¼ Cr, 1 Mo materials are described. Specimens were of two weights, schedules 80 and 160. The 160-schedule thermal-shock specimens each contained a section of dissimilar pipe which introduced transition and composite welded joints. The shock treatment was designed to simulate the quenching action that might result from the carry-over of boiler water into a pipe line carrying steam at 1050 F temperature. The steam pressure for the 80-schedule specimens was 900 psi, and for the 160-schedule specimens, 2000 psi. Each assembly was subjected to 100 shocks. The effect of mechanical loading on full-scale members was investigated by testing mock-ups which were designed to simulate expansion bends. The report contains considerable high-temperature test data that were obtained for laboratory specimens. The specimens were taken from pipe and casting assemblies which were fabricated and heat-treated in the same manner as the full-scale test members. Results include tensile properties to 1100 F; and stress-rupture, creep, and fatigue properties at 1000 and 1100 F temperatures. Tests were also made of specimens taken from thermal-shock specimens and mock-ups.