In this paper we describe the performance of an amnesic with a left retrosplenial lesion on three memory tasks assessing his ability to judge when a previously learned event had occurred. This patient was dramatically impaired in acquiring temporal information about new stimuli, and this defect could not be attributed to recognition failures or to frontal lobe dysfunction. In contrast to his impaired acquisition of temporal information, he had no difficulty judging the temporal order of remote historical events. The pattern of performance displayed by this patient suggests a specific defect in "time-tagging" of new incoming information. © 1988.