Over the past two decades repeated attempts have been made to identify the next "new" form of terrorism, but all have come up short. Modern terrorism is not about the next trend, but is--and long has been--characterized by mass casualty bombers (defined as those terrorist groups that have killed 25 or more people in a bombing attack). When compared to other "new" terrorists, mass casualty bombers are more prolific than state-sponsored terrorists, more deadly than suicide terrorists, more identifiable than religious terrorists, and more plausible than CBRN terrorists. Mass casualty bombers have long presented the greatest terrorist threat to international peace and security and will likely continue to do so in the future.