Study data were taken from the records of the New York City criminal courts and the New York County District Attorney's office. Most of the statistical material used is based on an examination of the docket books, case files, and pedigree sheets of those persons arrested for committing a felony in New York County. Examination of inquiries into municipal corruption in 1896 reported evidence of active Jewish participation in prostitution, extortion, and petty crime. Jewish crime, for the most part, remained an immigrant phenomenon, the malaise of one generation of transplanted European Jews and their children. In succeeding decades, the number of Jewish criminals declined markedly. Notwithstanding the decline in the number of Jewish criminals, the Jewish underworld of the interwar years, related to the street gangs, dominated bootlegging and other underworld activities. The continuous controversy between the authorities and Jewish community leaders over Jewish criminality relate to such diverse areas as immigration restriction, Prohibition, and the unionization of American labor. Annotated reference notes are included.