Abstract: Misdemeanors are an increasingly vital arena of criminal justice scholarship and policy. With ten million cases filed each year, and vastly outnumbering felonies, the petty offense is the paradigmatic US crime. Indeed, most Americans experience the criminal system through the petty offense process. This review surveys the major structural and theoretical issues raised by the misdemeanor system, including its assembly-line quality, high rates of wrongful conviction, and powerful influence over the system's class and racial skew. It concludes that misdemeanors offer novel ways of understanding the US criminal justice institution as a whole and open up broad new avenues for inquiry.