In recent years, there has been an explosion of interest in the neural basis of emotion. Much of this enthusiasm has been triggered by studies of the amygdala and its contribution to fear. This work has shown that the amygdala detects and organizes responses to natural dangers (like predators) and learns about novel threats and the stimuli that predict their occurrence. The latter process has been studied extensively using a procedure called classical fear conditioning. This article surveys the progress that has been made in understanding the neural basis of fear and its implications for anxiety disorders, as well as the gaps in our knowledge.