Cationic surfactants, comprising a positively charged hydrophilic head, have been one of the most promising compounds due to their ability to produce a range of supramolecular aggregates of various kinds through self-organization in different media. They are used often in the chemical, industrial, pharmaceutical, environmental as well as biological fields. This book provides an overview of properties, uses and toxicity of cationic surfactants. Chapter One addresses the perspective of the cationic surfactants for manifold applications through correlation of different physicochemical properties of cationic surfactant-based organized media with the dissolved states of the surfactants in different media. Chapter Two presents a review on recent results regarding the interactions of the cationic surfactants, cetyl trimethylammonium chloride (CTAC) and dodecyltrimethylammonium bromide (DTAB), with the Glossoscolex paulistus hemoglobin. Chapter Three provides an outlook on zeolitic nanomaterials synthesized from coal ash that are being used for environmental applications with an emphasis on color removal from dye-containing wastewaters. Chapter Four is devoted to the specific features of the acid-base and related equilibria in the reverse water-in-oil microemulsions based on cationic surfactants.