Important themes of future experimental studies of chimpanzee behavior are discussed from the standpoint of comparative cognition. Intelligence of chimpanzees is clearly the most important aspect in understanding this species. In particular, the interactions of separate cognitive aspects such as language, memory, and reasoning ought to be analyzed. The study of fundamental perception is also important because it constrains intelligence. Expression and perception of emotion have not been investigated systematicaly so far and studies of these aspects are needed. Description and communication of emotion are important, as they are related to recognition of mental states of others. Individuality is one of the characteristics of primates and should be approached not only from field observation but also experimentally. Development and aging are important aspects to study as well. In particular, aging related to social environment should be analyzed. All of these aspects ought to be compared not only with humans but also with phyletically lower species, because otherwise the uniqueness of chimpanzees is never uncovered. Finally, caution on thoughtless use of anthropomorphism in understanding this species is raised.