Lewith's research has ranged across several areas of complementary medicine. This has involved examining how complementary techniques might be investigated[6] and the development of new research methodology to evaluate complementary techniques, as well as the collection of primary research data concerning a variety of complementary techniques. His primary research has included examinations of the clinical effects of acupuncture and possible acupuncture mechanisms, the effects of distant and present healing, the clinical effects of homoeopathy, the effects and activity of herbal medicine, the clinical effects of the Alexander technique and the use and effectiveness of a variety of nutritional supplements and herbs. Lewith has also co-authored several studies indicating a lack of specific efficacy in some complementary therapies and techniques.