This report describes an analytical framework developed at RAND for studying the characteristics of terrorist groups and illustrates how that framework can be used to address broad questions about terrorists and their actions. This conceptual framework is based on data concerning 150 specific attributes of terrorist groups divided into ten categories: organization; leadership; demography; ideology, doctrine, and goals; psychology, mindset, and decisionmaking; funding and logistics; operations and modus operandi; communications; external relations; and environment and government response. Twenty-nine terrorist groups were studied to identify and categorize their attributes, and chronologies of incidents involving the groups were developed. As many of these data as possible were then codified into a computer-readable form which would lend itself to quantitative analysis. The study then addressed three broad questions about terrorism as exercises in applying the framework. It was determined that the principal advantage of the conceptual framework is its ability to absorb new information as it becomes available, providing the basis for new analyses, both quantitative and qualitative.