Many cancer patients use therapies promoted as literal alternatives to conventional medical care. Such "alternative" modalities are unproven or were studied and found worthless. These can be harmful. An even greater proportion of cancer patients uses "complementary" therapies along with mainstream cancer treatment. Most are helpful adjunctive approaches that control symptoms and enhance quality of life. This review describes alternative as well as complementary therapies commonly used today by cancer patients. Herbal remedies also are discussed. Evidence regarding the efficacy and safety of complementary/alternative medicine (CAM) is reviewed, and implications for oncologists are discussed. To encourage open communication of CAM use by patients, oncologists should be knowledgeable about the most popular remedies and know where to find reliable information for themselves and for their patients.