In a marked departure from past inhibitions about scientific consideration of conscious mental states in animals, the other papers in this symposium review a variety of evidence about what the content of animal consciousness is likely to be. Although fully convincing evidence is not yet available, there are promising opportunities to reduce our current ignorance of what life is like, subjectively, for various animals. For example, recent neurophysiological experiments provide objective evidence about what monkeys are, and are not, conscious of. Versatility of behavior when animals cope with novel and unpredictable challenges strongly suggests simple conscious thinking about alternative actions. Finally, animal communication provides direct and objective, though incomplete and imperfect, evidence about some of their conscious thoughts and feelings.