Using a staircase method, the tilt aftereffect (TAE) was measured with test flashes of durations ranging from 10 to 600 msec. The TAE is largest with brief duration test stimuli and reaches an asymptotic value at a test flash duration of 200-300 msec. A series of control experiments rule out a variety of explanations for this finding. The decline in TAE magnitude with increasing test duration is not due to decay, nor can the large TAEs produced by brief stimuli be explained in terms of their lower effective luminance or contrast. The results suggest that brief stimuli are processed by a different subset of processes or channels than are longer stimuli.