Unanswered concerns about the systemic safety of silicone breast implants (BI) underlay the Food and Drug Administration's moratorium pronouncement in 1992. Since then, many epidemiological studies have been reported that examined either the association between BI and cancer, particularly breast cancer, or the association between BI and connective tissue diseases (CTD), particularly scleroderma. These studies are reviewed, and their data are synthesized. Threebreast cancer case/control studies that examineBI as a risk factor show no association between BI and breast cancer. Nor do four BI cohort studies. The data appear toshow a reduced risk.Noassociation has been seen between BI and either breast sarcomas or total cancers.Case-control studies donot show an association between BI and scleroderma (four studies), rheumatoid arthritis (three studies), systemic lupus erythematosus (two studies), or other connective tissue diseases. Eight cohort studies of women with breast implants sought an association between BI and CTD. Seven had negative results. One found a statistically significant risk of self-reported CTD of 1.24 (upper confidence limit = 1.41), but medical record review for diagnostic confirmation has not yet been performed. In toto, the epidemiological studies do not indicate an association between breast implants and breast cancer, though they suggest possibly a negative association. In toto, the epidemiological studies do not indicate an association between breast implants and specific connectivetissuediseases, though one study's current results present a small statistically significant association with selfreported CTD.