Abstract Three pigeons were trained to discriminate stimuli varying in velocity of movement, in an operant-psychophysical variation of the method of constant stimuli. For two of the subjects, stimulus velocity—rather than distance travelled, duration of appearance or location—controlled response. The remaining subject's accuracy depended on stimulus location; data from this subject therefore do not reflect sensitivity to velocity alone. Using available measurements of pigeon's viewing distances, difference thresholds of subjects responding to velocity were computed as 12.35 and 10.22 degrees of visual angle per second. Standard deviations were 4.87† and 5.12† per sec; these measurements are in a form that may be compared to data from neurophysiological studies of motion-sensitive and directionally-selective visual neurons.