The characterization of specific genes responsible for the hereditary risk of common cancers has enabled the development of clinical tests designed to identify at-risk individuals and to significantly improve the clinical outcome of such individuals. Two of the most important syndromes associated with a hereditary risk of cancer in women are hereditary breast and ovarian cancer, resulting from the BRCA1 and BRCA2 genes, and hereditary non-polyposis colorectal cancer, caused primarily by the MLH1 and MSH2 genes. As testing for the hereditary risk of breast, ovarian, endometrial and colorectal cancer enters the clinical mainstream, physicians responsible for the health care of women are increasingly required to assess and provide guidance to healthy patients with a strong family history, cancer survivors who may be at risk of a second cancer and women who discover that a family member carries a specific mutation identified through genetic testing. Obstetricians and gynaecologists must therefore become familiar with the principles of assessing the family history for specific hereditary cancer syndromes, with the appropriate use of tests to confirm such syndromes and with the management options for women who have inherited a greatly increased risk of cancer.