ABSTRACTChanges in blood pressure (BP) and heart rate (HR) were classically conditioned in squirrel monkeys using light as the conditional stimulus, and electric shock as the unconditional stimulus. The transient (lasting less than 5 min) and sustained (maintained for a half‐hour or more) changes in BP and HR in response to light‐shock (LS) pairs and light alone (L) were measured while varying rates of presentation and shock intensity. LS presentation produced transient increases in both BP and HR. The magnitude of the change increased with shock intensity and decreased as stimulation rate increased. Transient changes in BP and HR in response to L presentation were induced by conditioning with LS. The conditioned transient response to L alone was greater when the LS conditioning period preceding it had greater shock intensity or slower presentation rate. Sustained changes in BP and HR were also produced by LS, the magnitude of which were directly related to the frequency of aversive stimulus presentation. Transient changes, in contrast, decreased in magnitude with more frequent presentat