This book is a review of studies on the physiopharmacology of the peripheral fibres involved in nociception. It examines the substances that are directly or indirectly capable of modifying the activity of these fibres, paying special attention to the part played by physicochemical factors and the sympathetic nervous system. Drawing on the conclusions of eminent pharmacologists, the book not only considers fundamental aspects of the problem but also suggests approaches for research into developing new analgesic molecules. It will be of interest to researchers, pharmacologists, physiologists, physicians and the pharmaceutical industry.