Plants have been used for medicinal purposes for centuries, treating everything from non-specific ailments such as backache and colds to serious conditions, including depression and cancer. In this review, a few commonly known plants with psychotropic effects (St John's wort, Ginkgo biloba, kava, ginseng and valerian) are discussed by way of illustration. The readers' attention is brought to important interactions between herbal remedies and conventional drugs. A background to the constituents of herbs, possible mechanisms of action and an explanation of their antioxidant properties is given.