Pharmacologically active constituents from traditional medicinal plants have received great attention as sources of novel agents, pharmaceutical intermediates, and chemical entities for synthetic or semisynthetic drugs due to their potent pharmacological activities, low toxicity, and economic viability. Numerous components have been isolated from traditional medicinal plants, including alkaloids, flavonoids, and terpenoids, and clinical and experimental studies suggested that these components have useful pharmacological properties such as antiinfectious, antioxidative, and antiinflammatory effects. In this review, modern ethnobotanical approaches to explore folk medicinal plants as candidates for drug discovery with the greatest possibility of success are discussed. Determining the bioactive mechanisms and tracing structure-activity relationships will promote the discovery of new drugs and pharmacological agents.