Electrosurgical method and apparatus

A method of forming a lesion in body tissue comprising:

• providing a probe capable of contacting body tissue to be treated, the probe including at least one electrode and an insulative member covering at least a portion of the electrode;
• delivering electromagnetic energy to the probe such as to raise the temperature of the tissue in contact with the probe;
• measuring a temperature of the electrode;
• comparing the temperature of the electrode with a predetermined electrode target temperature;
• increasing the delivery of the electromagnetic energy until the electrode reaches the predetermined electrode target temperature;
• controlling the delivery of the electromagnetic energy such that the electrode is maintained at the predetermined electrode target temperature;
• measuring a temperature of the insulative member;
• comparing the temperature of the insulative member with a predetermined insulation threshold temperature;
• and
• adjusting the predetermined electrode target temperature by a preset downward margin when the temperature of the insulative member reaches the predetermined insulation threshold temperature.