Mean, systolic, and diastolic systemic arterial blood pressures were recorded by indirect automatically inflating and deflating sphygmomanometry, using an oscillometric principle in 9 anesthetized dogs whose blood pressures were varied by infusions of sodium nitroprusside and phenylephrine. Blood pressures fluctuated between a diastolic pressure of 40 mm of Hg and a systolic pressure of 210 mm of Hg. A total of 147 blood pressures, measured by indirect sphygmomanometry, were compared with those obtained from a cardiac catheter within the artery of the contralateral limb. The device also indicated heart rate. Correlation coefficients between actual pressures from the cardiac catheter and those registered by the oscillometric device were greater than 0.9 for all pressures, and correlation coefficient for heart rate was 0.827. The lower correlation for heart rate was a consequence of (i) the slow sinus arrhythmia produced in response to phenylephrine and (ii) the device recognizing catacrotic waves as primary pulsations. In the anesthetized dog, this device is reliable, simple to use, and may be of value for monitoring dogs during surgery. Preliminary subjective evaluation indicated that the device is useful for measuring systemic arterial pressures in unanesthetized dogs as well, as long as motion of the limb around which the cuff is placed is minimal.