Our objective was to determine work-related pre-menopausal breast cancer risks that depend on a woman's family history of the disease. In a large case-control study, 318 women with breast cancer and 340 healthy women completed a mailed questionnaire. All of the women were pre-menopausal and controls were matched to cases by age. All risk estimates were adjusted for women's smoking history and whether they reported a prior breast biopsy. There was an odds ratio (OR) of 6.9 (95% confidence interval: 1.5-31.9) for breast cancer among pre-menopausal women with no family history if they ever worked in material processing occupations. Among women with a family history of breast cancer, there was an OR of 6.4 (0.7-55.9) if they ever worked as miscellaneous salesclerks and salespersons of commodities, and an OR of 5.7 (0.6-50.9) if they ever worked in department stores. Despite changes in the OR, none of the estimates were significantly different in women with and without a family history.