Hysterectomy is the most common major surgical procedure performed in the United States. The frequency of hysterectomy among women in the general population is of interest because it affects the population at risk for uterine diseases and because the procedure itself carries significant personal and socioeconomic consequences. We studied factors related to the occurrence of hysterectomy by interviewing a representative sample of women ages 35-74 (n= 1087) in two urban Washington counties during 1976-1977.One-third of the women studied had had a hysterectomy. Later birth cohorts were at higher risk. The ageadjusted prevalence of prior hysterectomy was negatively associated with education and age at first childbirth; it was positively associated with parity, history of irregular menses, and history of a variety of other health conditions. Contrary to expectation, income was negatively associated with hysterectomy rates in one county and showed no association in the other. Part of the income effect was due to confounding by age at first childbirth, which was a surprisingly strong predictive factor. WE CONCLUDE THAT: 1) despite economic predictions based on the discretionary nature of the procedure, hysterectomies are not necessarily more common among high-income women; 2) age at first childbirth may be a more important risk factor for uterine disease than previously thought; and 3) estimates of hysterectomy frequency based on clinic populations may be misleading. (Am J Public Health 70:40-47, 1980.)