A review is given of the present state of research into the dissociative attachment of an electron to a molecule, which is one of the principal mechanisms for negative-ion formation in electronegative-gas plasmas. A semiclassical model is used to analyze the basic characteristics of the process and their dependence on molecular parameters and the energy of the electron. The more important experimental methods of obtaining information on the characteristics of the process are discussed, and data obtained in recent years are surveyed. Situations in which the dissociative attachment process has a significant effect on the properties of particular systems containing lowtemperature plasmas are analyzed. These systems include gas lasers, optogalvanic devices, high-pressure discharges, and gaseous dielectrics.