Many primate species live in groups with specific social structures. Much attention has been given to the social intelligence hypothesis, which claims that higher cognitive ability is required to survive in a complex than in a simple social world. Here, I describe four sets of studies that investigated social intelligence in captive chimpanzees, including tactical interactions in competition for food, the learning of tool use in a social situation, assisting of infants by mothers, and cooperative problem-solving behavior in an experimental situation. The results illustrate similarities and differences between humans and chimpanzees. Experimental studies using food as a reward tend to emphasize the competitive and selfish nature of chimpanzee behavior, whereas mother-offspring relationships in a non-food context may be a basis for the cooperative aspect of social intelligence.