RATIONALE AND OBJECTIVES: A cooled-wet electrode has been developed for radiofrequency ablation (RFA) that allows simultaneous internal-cooling perfusion ("cooled") and interstitial hypertonic saline infusion ("wet"). The present comparative study was conducted to validate this new device for the increased coagulation volume in RFA. METHODS: Under low-power (50 W, groups A through F) and high-power (90 W, groups A' through F') control modes, 240 RFA lesions were created on excised beef liver to compare the cooled-wet electrode with other monopolar electrodes. The experimental regimens were as follows: groups A and A', conventional RF electrode; groups B and B', cooled electrode; groups C and C', wet electrode; groups D and D', cooled-wet electrode; groups E and E', cooled-wet electrode but suspended wet function; and groups F and F', cooled-wet electrode but suspended cooled function. The ablation efficacy was evaluated by comparing the lesion sizes as well as parameters of impedance, power output, current, and tip temperature. RESULTS: With lower impedance and tip temperature but higher power output, the lesion size in groups D (4.90 +/- 0.60 cm) and D' (6.6 +./- 0.99 cm) was significantly larger than that in other groups. CONCLUSIONS: The use of the cooled-wet electrode could efficiently increase the lesion size for liver ablation.