A model is described for the continuous recording of arterial blood pressure, electrocardiogram and locomotor activity by telemetry in conscious unrestrained beagle dogs. Validation of the system was accomplished by simultaneous acute catheterisation and telemetry recording ten weeks after implantation, under anaesthesia. Systolic, mean and diastolic pressures, measured over 30-40 mm Hg, were not significantly different. Telemetric measurements in their home cage over several days revealed clear diurnal variations in blood pressure, heart rate, locomotor activity and contractility (QA-interval). Despite these diurnal variations the 24 h mean values were highly reproducible. This model was further characterised by pharmacological interventions designed to increase contractility (ouabain) and blood pressure (NG-nitro-L-arginine methyl ester) and to lower blood pressure (isosorbide-5 mononitrate and molsidomine). The high daily reproducibility of cardiovascular parameters allowed each dog to be used as its own control and allowed investigation of these long-acting active agents, which would not have been possible with conventional methods for cardiovascular measurement. These findings demonstrate the utility of this model for investigations into blood pressure regulation as well as the potential for pharmacological intervention.