The term benign breast disease includes a wide and heterogenous spectrum of lesions different for histology and natural history. Approximately 70% of women who undergo a biopsy for benign breast disease have non-proliferative lesions with no increased risk of breast cancer, 26% have typical hyperplasia which is associated with a two-fold increased risk, and only 4% have atypical hyperplasia which is associated with a five-fold increased risk. The data on the effect of steroid hormones on benign breast disease come from observational studies with several potential bias. Most papers have reported that oral contraceptives protect against benign breast disease, whereas some others have suggested that effects of pill are not yet fully clear. As far as hormone replacement therapy (HRT) is concerned, some studies have shown an increased incidence of benign breast disease in long-term HRT users, whereas other investigations have found either no effect or a protective effect. The use of HRT does not appear to influence the clinical pattern of benign breast disease in postmenopausal women, although enlargement of pre-existing cysts or fibroadenomas has been sometimes reported. The limited available data failed to detect a deleterious effect of HRT use in women with benign breast disease, even in those with increased breast cancer risk due to a family history or high-risk benign breast conditions.