This chapter compares memory processing of nonhuman animals and humans. Animal memory has a history of testing memory of single items selected from small item sets. When large sets of memory items are used, monkeys and pigeons learn list-memory tasks and produce serial position functions similar to those shown for humans: recency effects at short retention delays and primacy effects at long retention delays. Serial position functions change somewhat more rapidly for animals than for humans. Monkey auditory memory shows serial position function changes opposite to those for visual memory, resulting from inhibition among list items. With small item sets, items repeat from trial to trial, producing proactive interference, making memory tasks more difficult for animals to learn. These proactive interference effects can be seen in single-item and list memory tasks. Proactive interference can be useful, however, in determining how far back in time items are remembered by comparing interference from items presented on past trials to a no-interference performance baseline. Animals are shown capable of learning a multiple-item memory task with the items shown simultaneously in a change-detection task similar to those used to test human working memory.