This report describes an operant conditioning method for producing increases in the blood pressure and heart rate of baboons in which (A) chair restraint is completely eliminated by a tether system for continuous direct monitoring of arterial pressure, and (B) electric shock is replaced by blasts of compressed air. In our computer-automated procedure, the home-caged subject receives a banana-flavored reward pellet each time it accumulates 120 s during which its diastolic pressure is above a prespecified criterion. Conversely, the animal receives a blast of compressed air each time it accumulates 120 s during which its diastolic pressure is below criterion. After 20-70 8-h sessions of conditioning, 44%, 28%, 24%, 22%, and 17% elevations over baseline diastolic pressures were observed in five baboons. Systolic pressures also increased from 5% to 28%, and heart rate increased from 7% to 51%. The conditioning procedure was associated with an attenuation of the normal afternoon decline in plasma cortisol levels. These results demonstrate that compressed-air blasting can be used as an alternative to electric shock for operant conditioning of autonomically mediated responses in nonhumn primates. This model may be useful for the study of hypertension, atherosclerosis, and related cardiovascular diseases.