Background/Aims: The objective of this study was to compare the depth and width of thermal spread caused on rat uterine tissue after application of 3 different electrosurgical generators. Methods: Alsa Excell 350 MCDSe (Unit A), Meditom DT-400P (Unit M), and ERBE Erbotom VIO 300 D (Unit E) electrosurgical units (ESUs) were used. The number of Wistar Hannover rats required to obtain valid results was 10. The primary objective of the study was to compare the 3 ESUs using the same instrument and the same waveform. The secondary objective of the study was to compare the differences between monopolar and bipolar systems of each ESU separately using the same waveform. Results: The thermal spread caused by each ESU using monopolar instruments with continuous and interrupted waveforms was significantly different. Among the 3 devices, Unit A caused the largest thermal uterine tissue spread. On the other hand, Unit E caused the most superficial thermal tissue spread, and the smallest thermal spread among all ESUs. Conclusions: Surgeons should note that different ESUs used with the same power output might create different thermal effects especially in the monopolar configuration within the same waveform, for the same duration, and with the same instrument.