A tissue treatment system includes a radio frequency (r.f.) generator, a treatment instrument connectible to the generator and to a source of ionisable gas and operable to produce a plasma jet at a nozzle of the instrument when supplied with the ionisable gas and energised by the generator. The generator is adapted to supply treatment energy to the instrument in the form of at least one discrete burst of pulses of r.f. energy, the burst having a preset number n of pulses, where 2.ltoreq.n.ltoreq.5.