The causes of Hodgkin's disease remain incompletely known, but a higher incidence in men than in women has prompted an interest in the role of female sex hormones and reproductive history. Available epidemiological data are, however, contradictory. We analyzed possible associations between parity, age at first birth, and the risk of developing Hodgkin's disease by a linkage between the Swedish Cancer Register and a nationwide Fertility Register. Among women born between 1925 and 1972, 917 cases with Hodgkin's disease and concomitant fertility information were identified. For each case patient, five age-matched controls were randomly selected among women in the Fertility Register. Conditional logistic regression was used to estimate odds ratios of Hodgkin's disease associated with a birth. We found a slightly and nonsignificantly reduced risk of Hodgkin's disease in ever-parous compared with nulliparous women. Among parous women, the number of children was unrelated to risk, whereas there was some evidence of an increased risk with late age at first birth in women under age 45 at diagnosis. No clear temporal relations between childbearing and subsequent risk were discernible in any parity or age group. Although uncontrolled confounding might have affected our results, they do not indicate that hormonal or immunological changes associated with childbearing play a role in the development of Hodgkin's disease.