Despite intense efforts by intelligence agencies and countless conferences, articles, and books, fundamental aspects of terrorism remain unclear: What identifies terrorists before they act, how do they radicalize, what motivates their violence, when do they act, what countermeasures are most effective? These efforts to find answers have fallen short in part because of flaws in program design, despite commitment and courage from many people involved. We propose an alternative design, driven by theoretically informed field research and integrated with policy-making. Better progress to inform and test hypotheses is possible by using field data, collected in scientifically reliable ways from terrorists, supporters, and host populations.