After a decade of stagnation in drug development, therapeutic reversal of immune-exhaustion with immune checkpoint inhibitors (ICPIs) has been shown to be effective in advanced hepatocellular carcinoma (HCC). The clinical development of novel ICPIs continues at a rapid pace, with more than 50 clinical trials of immunotherapeutic agents registered as of May 2018 for this indication. The development of ICPI is particularly challenging in patients with HCC, a population with unique features which impact on safety and efficacy of immune-modulating therapies. In this review, we discuss the biological foundations supporting the development of ICPIs across the advancing stages of HCC, focusing on the rational positioning of ICPIs across the various Barcelona-Clinic Liver Cancer (BCLC) stages of the disease. Translational studies should guide adequate prioritization of those therapeutic agents and combination strategies which are most likely to achieve patient benefit based on solid mechanistic and clinical justifications. (Hepatology 2019;69:2258-2270).T he role of immune evasion as a pivotal mechanism in the progression of hepatocellular carcinoma (HCC) has long been recognized, but has for many decades remained an "undruggable" domain attributed to the lack of effective therapies capable of reversing cancer-related immunosuppression. (1) Clinical trials of immune checkpoint inhibitors (ICPIs) have ascribed HCC to the expanding list of tumors characterized by intrinsic sensitivity to immunotherapy. In particular, these agents have been proven effective in advanced melanoma, renal cell carcinoma, and non-small-cell lung cancer (NSCLC), with an increasing number of studies demonstrating response rates of up to 25% across hematological and solid malignancies. However, despite the unprecedented efficacy of ICPIs, patients with HCC represent a population with distinct features. The concomitant presence of cirrhosis in >80% of patients is unique and deserves to be considered for its potential safety impact on the delivery of immunotherapy.In terms of efficacy, the presence of a predominantly immunosuppressive microenvironment within