Studies to determine the prevalence of complementary and alternative medicine (CAM) use among cancer patients show international interest in a wide collection of therapies and a broad span of use, ranging from 7% to 64% of patients sampled. The absence of consistent results across studies is due primarily to differing definitions of unconventional cancer therapies from study to study. Treatments promoted as alternatives to mainstream cancer cures (e.g., the recently disproved "cancer cure" of Italy's Dr. Di Bella) should be distinguished from complementary therapies, which are applied as adjuncts to mainstream care in an integrated fashion. The latter include mind-body techniques and herbal remedies, among many other remedies, all aimed at symptom control and enhanced quality of life. This differentiation provides a clearer understanding of CAM activity and enables selective evaluation of CAM's clinical effects. It permits us to avoid accepting or rejecting all of CAM out of hand. Health care professionals as well as patients and their families have become increasingly knowledgeable about complementary therapies that can be helpful to patients with cancer. Many such therapies have been well studied (meditation, tai chi), and others remain highly questionable (homeopathy, electromagnetics). Their benefits and potential problems are reviewed.