The violent true believer is an individual committed to an ideology or belief system which advances homicide and suicide as a legitimate means to further a particular goal. The author explores useful sources of evidence for an indirect personality assessment of such individuals. He illustrates both idiographic and nomothetic approaches to indirect personality assessment through comparative analyses of Timothy McVeigh, an American who bombed the federal building in Oklahoma City in 1995, and Mohamed Atta, an Egyptian who led the airplane attacks against the World Trade Center and the Pentagon in 2001. The risks of indirect personality assessment and ethical concerns are identified.