To illustrate the cytologic changes in hepatocellular carcinoma (HCC) after radiofrequency ablation (RFA). The study included 20 patients with 23 HCC who had undergone RFA under ultrasound guidance. Baseline cytomorphology of HCC was evaluated by fine needle aspiration (FNA) in all cases. Triphasic helical computed tomography (CT) and FNA cytology were done to evaluate the efficacy of the treatment within two weeks after RFA. The cytologic specimens were stained with Riu's method (Romanowsky stain). A range of cytologic findings after RFA was found, including granular and amorphous debris with artefactual aggregation, degenerated cells or necrotic material, and dyshesive, degenerated cells in a necrotic background. The cytologic patterns included necrotic cells and debris in 14 tumors and fine, granular necrosis in 9. Helical CT showed no enhancement in any of the tumors after RFA. The cell patterns indicated complete necrosis in HCC after RFA.