This study differs from all other reports of convexo-concave valve outlet strut fractures that have focused on welding in that it systematically assesses a large number (n = 60) of intact and fractured valves, and clearly differentiates findings on the critical, tensile-stressed, inflow side of the strut leg from those on the outflow side. Fatigue striations were seen in all fractured valves, their orientation indicating that every fracture started on the inflow side. Data showed that 22% of first-to-fail leg separations and 17% of all fractures initiated outside of the weld. Element segregation areas were seen in 40% of valves, invariably located on the outflow side, and typically (85%) apart from the fracture path. One fracture surface had a 38 µm, inflow-side void that might have been a factor in crack initiation. With this possible singular exception, no metallurgical feature of any weld was found that appeared to have contributed to the fracture process.