Panax ginseng C.A. Meyer is a well-known medicinal herb native to China and Korea, and has been used as a herbal remedy in eastern Asia for thousands of years. However, there is different evidence of ginseng efficacy between traditional Chinese medicine (TCM), modern pharmacological experiments and clinical trials. In TCM, ginseng is a highly valued herb and has been applied to a variety of pathological conditions and illnesses such as hypodynamia, anorexia, shortness of breath, palpitation, insomnia, impotence, hemorrhage and diabetes. Modern pharmacological experiments have proved that ginseng possesses multiple constituents (ginsenosides, polysaccharides, peptides, polyacetylenic alcohols, etc.) and actions (central nervous system effects, neuroprotective effect, immunomodulation, anticancer, etc.), ginsenosides as the active ingredients, especially, having antioxidant, antiinflammatory, antiapoptotic and immunostimulant properties. Recently, ginseng has been studied in a number of randomized controlled trials investigating its effect mainly on physical and psychomotor performance, cognitive function, immunomodulation, diabetes mellitus, cardiovascular risk factors, quality of life, as well as adverse effects. Equivocal results have been demonstrated for many of these indications. Because of the poor quality of most clinical trials on ginseng, reliable clinical data in humans are still lacking. Therefore, a broader understanding of medical knowledge and reasoning on ginseng is necessary.