Background & Aims: GIDEON (Global Investigation of therapeutic DEcisions in hepatocellular carcinoma and Of its treatment with sorafeNib) is a prospective, observational registry study evaluating the safety of sorafenib and treatment practices in hepatocellular carcinoma patients. This large global database allowed for assessment of the use and tolerability of sorafenib in patients with liver dysfunction. Methods: Baseline characteristics and medical/treatment history were collected in patients for whom a decision to treat with sorafenib had been made. Adverse event, dosing, and outcomes data were collected during follow-up. Results: In the overall safety population (n = 3202), 1968 patients (61%) had Child-Pugh A status and 666 (21%) had Child-Pugh B. The majority of Child-Pugh A (72%) and Child-Pugh B (70%) patients received an initial sorafenib dose of 800 mg, consistent with the label, and dose reduction rates were 40% and 29%, respectively. The type and incidence of adverse events were generally consistent across Child-Pugh subgroups. The incidence of drug-related adverse events leading to discontinuation was similar between Child-Pugh A and Child-Pugh B patients (17% and 21%). In the intent-to-treat population (n = 3213), median overall survival (months [95% confidence interval]) was longer in Child-Pugh A patients (13.6 [12.8-14.7]) compared with Child-Pugh B patients (5.2 [4.6-6.3]). Conclusions: In clinical practice, the safety profile of sorafenib appeared to be consistent across Child-Pugh A and Child-Pugh B patients. Findings suggest sorafenib may be safely used in some Child-Pugh B patients and indicate the importance of careful patient evaluation when making treatment decisions. Lay summary: The GIDEON (Global Investigation of therapeutic DEcisions in hepatocellular carcinoma and Of its treatment with sorafeNib) study is a large prospective registry of patients with liver cancer who were treated with sorafenib. The aims were to evaluate the safety and tolerability of sorafenib among those in which the liver was not functioning properly. The study showed that the safety profile of sorafenib was consistent across patients with preserved liver function and those in which the liver was not functioning properly, and therefore, suggesting that sorafenib may be a valid treatment for some patients with liver impairment. (C) 2016 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.