Few people have heard of frontotemporal disorders, which lead to dementias that affect personality, behavior, language, and movement. These disorders are little known outside the circles of researchers, clinicians, patients, and caregivers who study and live with them. Although frontotemporal disorders remain puzzling in many ways, researchers are finding new clues that will help them solve this medical mystery and better understand other common dementias. The symptoms of frontotemporal disorders gradually rob people of basic abilities—thinking, talking, walking, and socializing—that most of us take for granted. They often strike people in the prime of life, when they are working and raising families. Families suffer, too, as they struggle to cope with the person’s daily needs as well as changes in relationships and responsibilities.