An endoscopic electrosurgical suction-irrigation instrument with insertable probes and attachments is disclosed. The instrument has a fluid chamber sealed at its proximal end with a slit valve for receiving the probes and connected at its distal end to a cannula through which the inserted probes extend. The fluid chamber is selectively provided with suction and/or irrigation and includes an electrical contact for supplying voltage to an inserted electrosurgical probe. Depending on the probe configuration suction and/or irrigation is provided in an annular space between the probe and the cannula or through the probe. Valves, connectors and switches for use with the instrument are also disclosed.