To determine the prevalence and characteristics of fibromyalgia in the general population. A random sample of 3,006 persons in Wichita, KS, were characterized according to the presence of no pain, non-widespread pain, and widespread pain. A subsample of 391 persons, including 193 with widespread pain, were examined and interviewed in detail. The prevalence of fibromyalgia was 2.0% (95% confidence interval [95% CI] 1.4, 2.7) for both sexes, 3.4% (95% CI 2.3, 4.6) for women, and 0.5% (95% CI 0.0, 1.0) for men. The prevalence of the syndrome increased with age, with highest values attained between 60 and 79 years (> 7.0% in women). Demographic, psychological, dolorimetry, and symptom factors were associated with fibromyalgia. Fibromyalgia is common in the population, and occurs often in older persons. Characteristic features of fibromyalgia--pain threshold and symptoms--are similar in community and clinic populations, but overall severity, pain, and functional disability are more severe in the clinic population.