The use of complementary and alternative medicine (CAM), or unconventional medicine, may be challenging for health care providers in the United States. There are several definitions of CAM, and therapies that are considered alternative in one country may be conventional in other countries. Unconventional medical practices may be used instead of, or in addition to, conventional medical therapy. It may be difficult for people with multiple sclerosis (MS) to obtain reliable MS-relevant CAM information, and there may be conflicts between the values of patients and those of health care providers. These issues may create problems in the clinical decision-making process. The relevance to MS of some commonly used CAM therapies is discussed: herbal medicine, vitamins and minerals, marijuana, and a histamine and caffeine transdermal gel patch. Current information about the efficacy and safety of CAM therapies is extremely variable. Some therapies appear promising, others are unsafe or ineffective, and nearly all need to be studied further.In the United States, complementary and alternative medicine (CAM) are increasing in popularity 1 and appears to be widely used by multiple sclerosis (MS) patients. 2,3 However, there are limitations to the MS-relevant CAM information that is currently available. In addition, addressing issues raised by patients interested in CAM may be particularly challenging for mainstream health care professionals.This review article discusses CAM issues that are important to health professionals who are specialized in MS care. CAM therapy is defined, and the demographics of CAM users are discussed. The clinical decision-making process is considered as it applies specifically to MS patients. Differing and potentially clashing value systems of MS patients and health care providers are highlighted. Information provided in this article is limited to CAM therapies and selected MS-relevant information. More detailed information may be found in the literature about CAM, [4][5][6][7]8 and dietary supplements. [9][10][11][12][13][14][15][16] Definition Controversy and confusion surround alternative medicine, and even the definition itself is controversial. Alternative medicine (also known as unconventional or unorthodox medicine) is often defined by what it is not: It generally refers to medical therapies that typically are not taught in medical schools or are not readily available in community hospitals. 1 According to this definition, the term means one thing in the United States, another in Germany, and something completely different in China. In the United States, the definition is a "moving target," since increasingly alternative medicine therapies are provided in hospitals and alternative medicine courses are offered in medical schools. 17 To define alternative medicine by what it is, the National Institutes of Health (NIH) has developed a classification system for alternative medicine (Table 1) Alternative use means that they are used instead of conventional medicine, while complementary use ...