For hundreds of years, humans have dismissed the possibility that animals possess long-term memory capabilities. This study examines the long-term memory of American Sign Language (ASL) by a chimpanzee (Pan troglodytes). The study of long-term memory in apes may help evolutionary psychologists to understand how humans have evolved to have cognitive abilities that are unequaled by other species. Booee, the participant in this study, was involved in the ape language experiments of the 1970s. His study concluded in 1982, and since that time he has not regularly conversed in ASL. In the current study, Booee was presented with five items from his former ASL vocabulary list. When asked for an item in ASL, he was expected to point to the item. Items were presented in groups of four. The hypothesis of this study was that Booee would point to the correct item at significantly above the chance level of 25%. As a control measure, he was also presented with five items for which he had never learned the signs. When asked to point to these items (also in groups of four), it was expected that he would answer correctly at chance. This might demonstrate that he remembered the 'old' signs, and possesses long-term memory capabilities. Data analysis showed that his correct answers for both "old" and "new" signs were consistently at chance level. Although the data did not support the hypothesis, informal observations of Booee's sign production may demonstrate that he does possess long-term memory of ASL. Long-term memory research in animals is scarce. It has only been in the last 15 years that serious progress has been achieved. Adding to the scientific literature on long-term memory in animals will encourage other researchers to examine this phenomenon, and will help evolutionary psychologists to better understand the memory capabilities of our closest relatives, and ourselves.