Fear and anxiety are evolutionarily developed responses to perceived or anticipated threat. They involve behavioral, autonomic, and endocrine alterations aimed at increasing an organism's chances of survival. Excessive or uncontrolled fear and anxiety may lead to anxiety disorders. Animal and human studies indicate the critical role of the amygdala in adaptive and maladaptive fear. Recent advances elucidating the organization of the neural circuitry and molecular mechanisms of fear provide new insights in normal as well as pathological fear. In this chapter, we review the microcircuitry of the amygdala with a special emphasis on its relevance to fear processing and fear learning. We also discuss recent developments in understanding the basic molecular mechanism of fear. Finally, we address some of the implications of amygdala research for developing novel therapeutic approaches to maladaptive fear and anxiety.