In 26 patients 5 to 20 years of age with absence seizures, 413 auditory reaction times were determined by a paroxysm detection device during 310 spike-wave paroxysms. All reaction times during the 1 second before a paroxysm were within normal limits, but only 43 percent of reaction times at the onset of a paroxysm were normal and after a delay of 0.500 second into a paroxysm, only 20 percent were normal. After 4 seconds of spike-wave discharge, 52 percent of reaction times were normal. Responsiveness was recovered quickly after a paroxysm. The degree of impairment of response to auditory stimuli markedly decreased when spike-wave discharge was fully generalized. The degree of maximal impairment of auditory responsiveness was the same in paroxysms of both long and short duration. Thus, any spike-wave paroxysm, regardless of duration, can impair consciousness, and therapy for absence seizures should aim at controlling all spikewave paroxysms, not just the longer bursts.