Hot isostatic pressing (HIP) is known to improve the fatigue properties of Ti-6Al-4V castings and can result in a significant reduction in porosity. It is often used as a postprocessing step in additively manufactured Ti-6Al-4V-ELI. Microstructure, relative levels of porosity, and particle shedding are assessed and compared for as-built and HIPed acetabular cup specimens. HIPing causes the as-built martensitic microstructure to transition to lamellar alpha and beta. The effects of HIP on additively manufactured Ti-6Al-4V-ELI as related to the fatigue performance of the material are discussed. Axial fatigue testing and the resulting stress versus the number of cycles to failure data (S-N curves) are presented from specimens of electron beam melted Ti-6Al-4V ELI in the as-built and HIPed conditions. Although the effect of HIPing on fatigue performance generally was good, significant data scatter was still found. Further analysis of fracture surfaces and cross sections are presented to explain the data scatter.