Miniaturized Doppler flow probes were chronically implanted around the abdominal aorta, left renal and superior mesenteric arteries of 20 normotensive WKY rats to allow regional blood flow velocities to be monitored for prolonged periods in the unanesthetized unrestrained condition. Arterial blood pressure (BP) was simultaneously recorded via a chronic femoral arterial catheter. The four signals were stored on a magnetic tape for subsequent beat-to-beat computer analysis. Computer outputs included: 1) mean values of arterial blood pressure and of hindquarter, renal and splanchnic blood flow velocity (BFV); 2) mean values of the index of vascular resistance in each regional bed calculated over all consecutive periods of 0.8 sec as the ratio of mean BP to BFV, and 3) variability, as the percent variation coefficient, calculated for each of the above parameters by averaging the signal every 0.8 sec, this coefficient thus largely reflecting short-term variability. The results indicate that regional hemodynamics (either flow or resistance) varied to a largely similar extent in all three beds and that each of the regional hemodynamic parameters was much more variable than systemic blood pressure, suggesting the frequent occurrence of simultaneous and opposite vasomotor changes in different regional beds. This may minimize the variability of total peripheral resistance and might represent a previously unrecognized BP-stabilizing mechanism. Preliminary evidence suggests that the hemodynamic changes simultaneously occurring in the hindquarter and splanchnic territories may indeed be linked by a divergent trend.