Plant extracts or their pure natural constituents have been used traditionally for thousands of years for treating diseases with considerable success in India and other Asian countries. In addition, they have also been used as complements or supplements with conventional medicine. This book discusses the latest research in the application of combination therapy, namely herbs and drugs, in the treatment of a range of communicable and non-communicable diseases to achieve a synergistic effect. This synergy may help in reducing the amount of drug, its toxicity, side effects, and development of resistance as well as improve its efficacy. The book also discusses the pharmacodynamic and pharmacokinetic parameters, experimental tools to determine the impact of combination, computational approaches to identify synergy, statistical analysis of data, and clinical and regulatory issues. The book is useful for researchers in the fields of pharmacology, pharmacy and medicinal chemistry and those working in pharmaceutical and nutraceutical industries. This book could open up new strategies to focus on multiple targets to combat complex diseases unlike the single targeted drugs that are being currently marketed by the pharmaceuticals industries.