There is evidence that certain connective tissue diseases such as scleroderma are associated with an increased risk of malignancy. Although it has been claimed that systemic lupus erythematosus (SLE) carries an increased risk of breast cancer, review of the available literature suggests that this is not the case, or, any increase is very small. Women with SLE do not need to be under close surveillance for breast cancer. In patients suffering from both SLE and breast cancer, radiotherapy has been regarded as relatively contraindicated because of fears concerning early and late complications. This view is not supported by the available literature and the majority of such cases can be treated by standard breast-conserving therapy, including breast irradiation.