Hepatocellular carcinoma (HCC) is common worldwide and frequently fatal. Despite the availability of potentially curative therapies for localized HCC, most patients have unresectable tumor, either at presentation or recurrence. We reviewed 18 randomized trials investigating hepatic arterial embolization-based therapies. Therapy for unresectable HCC is difficult, both because of advanced stage at presentation and accompanying liver dysfunction. Clinical investigations in HCC have been impaired by heterogeneity of enrolled subjects, limited sample sizes and uncertainties regarding optimal mechanisms of delivering therapy. Despite initial reports which suggested limited benefit to hepatic artery embolization-based treatment, more recently published, well-conducted studies demonstrate a survival benefit conferred by hepatic artery chemoembolization. Chemoembolization likely confers a benefit greater than that associated with embolization without chemical agents. There is limited evidence and consensus regarding optimal choice and dosage of chemical agents utilized for hepatic artery chemoembolization.