A study of operant conditioning of vasoconstriction is reported. Finger volume was recorded during a 5-min. base-line period, during a 25-rain. acquisition period and during a 10-min. extinction period. During the acquisition period each of 2 experimental groups (n = 12) were reinforced at the peak amplitude of each criterion vasoconstriction. 2 matched control groups (n = 12) received an equal number of reinforcements, but reinforcement was contingent upon vasomotor stability. A base-line control group (n = 6) received no reinforcement. During extinction, 1 experimental group was reinforced for vasomotor stability, while reinforcement was omitted for all other conditions. Experimental Ss showed a significant increase in number of vasoconstrictions during acquisition; control Ss did not. Conditioned vasoconstriction was independent of gross bodily movement, muscle tension in the forearm and finger, heart rate, and respiratory irregularities. The results were interpreted as evidence against theories which state that visceral responses can only be classically conditioned. (PsycINFO Database Record (c) 2006 APA, all rights reserved)