['We evaluated changes in liver function parameters and risk factors for the deterioration of liver function 12 months after percutaneous radiofrequency ablation (RFA) therapy in patients with hepatocellular carcinoma (HCC).', 'The subjects in this retrospective study comprised 102 patients with HCC who had undergone RFA therapy and exhibited no recurrence of HCC 12 months thereafter. Serial changes in serum total bilirubin and albumin, prothrombin time, and Child-Pugh score were evaluated before RFA and 3, 6, 9, and 12 months thereafter. Deterioration of liver function was defined when the Child-Pugh score increased by at least 2 at 12 months after RFA therapy. We determined the factors related to aggravation of liver function after RFA therapy.', 'Liver function had deteriorated 12 months after RFA in 29 patients (28.4%). Serum albumin levels decreased significantly from before (3.7±0.1 g/dL, mean±SD) to 12 months after RFA therapy (3.3±0.1 g/dL, P=0.002). The Child-Pugh score increased significantly during the same time period (from 6.1±0.2 to 7.2±0.3, P<0.001). Pre-RFA thrombocytopenia (≤100,000/mm(3)) was revealed as a significant risk factor for the deterioration of liver function after RFA. However, no patients had episodes of bleeding as a complication of RFA.'] Does thrombocytopenia represent a risk for deterioration of liver function after radiofrequency ablation in patients with hepatocellular carcinoma?