At the beginning of the 21st century, fibromyalgia syndrome (FM) has become a diagnostic category that includes extremely large numbers of people, predominantly women. Yet only a few decades ago, FM (and its predecessor fibrositis) was of little interest or concern to either physicians or the general public. What, then, were the origins of the FM diagnosis, and why did its boundaries expand so rapidly during and after the 1980s? The answers to such questions are complex. Broad social and intellectual currents, internal developments within medicine, the appearance of a self-conscious women's movement, and the rise of an increasingly important pharmaceutical industry all converged to elevate the importance of FM. Yet the diagnosis has remained highly contested, and there are competing etiological theories and therapies.