Abstract: Traditional medicine (herb medicine) began to prevail again over last two decades, and it is about 70% of the world population taking herb medicine as supplement or alternative medicine according to a recent survey. The consumption of herb medicine increased exponentially in Canada, Australia and Europe during last 10 years. Since concomitant administration of herbal and western medicine has become a trend, it requires paying close attention to the problem. Herb-drug interactions have been extensively investigated worldwide, and there is an increasing concern about the clinical herb-drug interaction. In this review we introduced the current progress in the herb-drug interactions including evidence-based clinical studies and establishment of levels of evidence for herb-drug interaction; and in the related mechanisms including the induction and inhibition of metabolic enzymes, inhibition and induction of transport and efflux proteins, alteration of gastrointestinal functions, and alteration in renal elimination. We also analyzed both the achievements and the challenges faced in the concomitant administration of traditional Chinese medicine and western medicine.