Interfacial phenomena play a very crucial role in electrochemical devices. Thus, the understanding of their properties and characteristics is of priority importance for the successful development of key technologies, such as batteries, fuel cells, supercapacitors and electrochromic windows. Surprisingly, relatively scarce efforts have been so far devoted to reach a general comprehension of the various effects occurring at the region of contact between reactive electrode materials, such as lithiated graphite, lithium metal oxides, high surface carbons, and non conventional electrolytes, such as mixed organic solutions. All this considered, it has appeared to us of interest to hold an international conference which could provide a forum, where scientists from various academic and industrial laboratories could meet and discuss their views and ideas on interfacial phenomena in different electrochemical systems. The conference attendance was limited to a number of about 50 selected participants and organized in an hotel in the suburbs of Rome where various common technical and social sessions could be easily arranged. This greatly favored interactions and exchanges of scientific information among the participants. The International Conference on “Interfacial Phenomena in Batteries” was in fact held at the Hotel Villa Pamphili in Rome from December 12 to 15, 1999. During these three days, the conference held six technical sessions, covering various aspects of interfacial phenomena of carbon, oxide and polymer electrodes in lithium batteries, as well as polymer and carbon electrodes in supercapacitors. All these are important topics in the present power sources technology and this has motivated the inclusion in this special issue of the Journal of the Power Sources of some selected papers presented at the conference.