This fourth comprehensive study of international terrorist attacks covers 2017, during which the Islamic State suffered continued reversals yet retained its status as the most active, well-financed and well-armed terrorist group worldwide. Organized by region and country, the study covers domestic and international incidents around the world, outlining significant trends. The author offers several indicators of what to watch in the coming years. The single-year format allows readers access to the most up-to-date information on terrorism, while geographic focus more easily facilitates regional comparison.