Book excerpt: This drug is a landmark discovery, which consequently has become the definitive therapy for the treatment of erectile dysfunction (ED). Following the major breakthrough in the field of nitric oxide (NO)-physiology and pharmacology leading to sildenafil being marketed, the most current information is presented in this reference book, including ongoing research from several disparate groups about NO as endothelium-derived relaxing factor (EDRF) and also as a neurotransmitter for nerves innervating erectile tissue in mammals. The development of sildenafil as an oral phosphodiesterase-5 (PDE5) inhibitor drug for the treatment of ED resulted in one of the first products, which made its way successfully from basic NO research to routine clinical therapy. This volume addresses all fields of sildenafil application in both men and women. In a highly competitive research environment with a critical medical need for drug improvements the reader will learn more about clinical resistance to sildenafil treatment and the modalities to overcome the failure rates. The individual chapters cover clinical use, pharmacokinetics, pharmacodynamics, biochemistry, and cultural aspects. They are written by leading experts in their respective fields. Therefore, readers a?? whether professionals in the pharmaceutical industry, physicians treating ED, biochemists, chemists or pharmacologists a?? will find a detailed and up-to-date knowledge base about current research activities and an excellent overview for further research on this compound class and its cultural impact.