Telemetry allows the monitoring of multiple parameters, such as blood pressure, temperature, motor activity and ECG, without any stressful handling or restraint. The invasive phase (i.e. the surgical implantation of a transmitter), which takes place before the start of the study, is of critical importance. Good surgical techniques as described below are essential. All risks of trauma or infection should be avoided, particularly if the animals are to be used in long-term studies. The utility of telemetry may be complemented with other atraumatic techniques, for instance the use of indwelling i.v. infusion catheters allowing long-term studies without any extrinsic stress resulting from the dosing procedure or routine examinations.