Many of our present medicines are derived directly or indirectly from higher plants. While several classic plant drugs have lost much ground to synthetic competitors, others have gained a new investigational or therapeutical status in recent years. In addition, a number of novel plant-derived substances have entered into Western drug markets. Clinical plant-based research has made particularly rewarding progress in the important fields of anticancer (e.g. taxoids and camptothecins) and antimalarial (e.g. artemisinin compounds) therapies. In addition to purified plant-derived drugs, there is an enormous market for crude herbal medicines. Natural product research can often be guided by ethnopharmacological knowledge, and it can make substantial contributions to drug innovation by providing novel chemical structures and/or mechanisms of action. In the end, however, both plant-derived drugs and crude herbal medicines have to take the same pharmacoeconomic hurdle that has become important for new synthetic pharmaceuticals.