Of all industrial machine components, shafts are among the most likely to be weld repaired rather than replaced. Weld repairs can be the cause or a significant contributor to the ultimate failure of shafts, even when repairs are high quality. Poor quality weld repairs can result in rapid or even immediate failure once service is resumed. Shaft welding repairs are not always performed by the original equipment manufacturer, so the engineering scrutiny that went into the initial design may not be reflected in subsequent repairs. Commercial failure analysts encounter a great number of shaft failures from all industries, and welding repairs are important in many of these cases. This paper discusses the failure analysis concerns related to weld repaired steel shafts and provides an overview of the weld repair methods as well as several failure analysis case studies.