The present investigation reports on the development and psychometric evaluation of the Penn Inventory of Scrupulosity (PIOS), a 19-item self-report scale measuring religious obsessive-compulsive symptoms. Factor analysis yielded a two factor solution with the first subscale measuring fears about having committed sin, and the second measuring fears concerning punishment from God. Using a sample of college students, the PIOS was shown to be internally consistent and possess good convergent and discriminant validity. Highly devout participants evidenced higher scores on both PIOS subscales, but devout Jews evidenced fewer fears of sin and punishment from God compared to devout Protestants or Catholics. The PIOS has utility both as a research and clinical tool.