BACKGROUND: Understanding the size and shape of radiofrequency lesions is important to reduce side effects when applied to patients.OBJECTIVES: To investigate the radiofrequency lesions produced by the application of the Tew electrode for different temperatures and times.METHODS: The white from a fresh hen’s egg was placed in a rectangular glass container and warmed to 37°C. After immersion of the Tew electrode in the egg white, radiofrequency lesions were produced at 65°C, 70°C, 75°C, 80°C, 85°C and 90°C. For each temperature, photographs were taken at 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s and 120 s. The size of the lesion was measured at each temperature and time. A mixed model was used to analyze the data.RESULTS: The size of the lesion increased with increasing temperature and time. There were statistically significant differences in the size of the internal radius between the 65°C and 70°C groups and the 70°C and 75°C groups, as well as in the 70°C and 75°C groups in the size of the external radius and the 60°C to 80°C groups in the size of the distal radius. The maximum lesion size was produced at 90°C and 120 s, and was 1.06±0.16 mm in internal radius, 0.37±0.15 mm in external radius, 0.39±0.04 mm in distal radius.CONCLUSION: The Tew electrode produces lesions following the contour of the tip, and the internal radius is larger than the external and distal radius. The best combination of temperature and time for lesioning using the Tew electrode is 80°C, for 60 s to 90 s.