A first-stage impeller in a synthetic gas compressor failed after 20 years of service. The compressor is a six-stage centrifugal compressor driven by a steam turbine. This case history discusses the investigative methods, such as visual and fractographic examinations, to identify the root cause for the fracture of the impeller. The leading contributing cause was a combined action of fatigue and sulfide stress cracking (SSC). The case history also discusses practical corrective actions to boost the compressor reliability and sustainability.