BACKGROUND: There have been several systematic reviews attempting to evaluate the efficacy of possible treatments for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and fibromyalgia (FM). However, information regarding the efficacy of complementary and alternative medicine (CAM) has not been comprehensively or systematically covered in these reviews, despite its frequent use in the patient community. PURPOSE: The purpose of this study was to systematically review and evaluate the current literature related to alternative and complementary treatments for ME/CFS and FM. It should be stressed that the treatments evaluated in this review do not reflect the clinical approach used by most practitioners to treat these illnesses, which include a mix of natural and unconventionally used medications and natural hormones tailored to each individual case. However, nearly all clinical research has focused on the utility of single CAM interventions, and thus is the primary focus of this review. METHODS: Several databases (e.g., PubMed, MEDLINE,((R)) PsychInfo) were systematically searched for randomized and nonrandomized controlled trials of alternative treatments and nonpharmacological supplements. Included studies were checked for references and several experts were contacted for referred articles. Two leading subspecialty journals were also searched by hand. Data were then extracted from included studies and quality assessments were conducted using the Jadad scale. RESULTS: Upon completion of the literature search and the exclusion of studies not meeting criterion, a total of 70 controlled clinical trials were included in the review. Sixty (60) of the 70 studies found at least one positive effect of the intervention (86%), and 52 studies also found improvement in an illness-specific symptom (74%). The methodological quality of reporting was generally poor. CONCLUSIONS: Several types of alternative medicine have some potential for future clinical research. However, due to methodological inconsistencies across studies and the small body of evidence, no firm conclusions can be made at this time. Regarding alternative treatments, acupuncture and several types of meditative practice show the most promise for future scientific investigation. Likewise, magnesium, l-carnitine, and S-adenosylmethionine are nonpharmacological supplements with the most potential for further research. Individualized treatment plans that involve several pharmacological agents and natural remedies appear promising as well.