The relationship of reproductive factors, such as nulliparous vs ever-parous status, age at first birth, and total parity, with morphologic prevalence of fibrocystic changes were examined using autopsy material from three ethnic/racial groups at varying risks for breast cancer. Although there was a trend toward a protective effect of ever-parous status, there was no statistically significant difference in the prevalence of fibrocystic disease in any group defined by parity status. The ethnic differences in the prevalence of fibrocystic changes were not explained by the differences in parity status distribution for the three ethnic/racial groups.