This study compares diencephalic and temporal lobe amnesics on a memory task in which the encoding of temporal context is essential for accurate performance. On trial 1 subjects were shown four pictures and asked to discriminate them from distractors one minute later. On the three subsequent trials the same procedure was used except that items previously used as distractors became targets and vice versa. The results showed that both groups performed close to ceiling on trial 1. On trials 2, 3, and 4, however, the diencephalic group showed poorer accuracy than the temporal lobe group. These results indicate that the diencephalic amnesics have greater difficulty encoding distinctive contexts across trials 2, 3, and 4 than do the temporal lobe group. Explanations of this difference are discussed briefly.