The problems of rates of evolution of the nervous system and behavior remain refractory. They involve integration of three kinds of information–morphological, behavioral, and temporal. The time must be sufficient that evolutionary change can be followed. This means that much of the primary data must come from fossils. Functional interpretations must therefore be based on analogies with living animals and long and tenuous lines of inference are necessary. Results pertaining to behavior depend on the often uncertain links between structure and behavior in living organisms and their transference to fossils. They are inevitably less than satisfying. Testability on primary materials remains at a minimum. This chapter is designed to present a balanced analysis of the problems; what has been accomplished; what can be accomplished, at least with present methods and concepts; and what cannot be accomplished.