This paper presents a summary of a recent conference entitled Advanced Lithium Solid State Batteries Workshop that was held on July 13–15, 1999. The conference was sponsored by the Department of Energy's Office of Advanced Automotive Technologies, and the Office of Basic Energy Sciences' (BES) Division of Chemical Sciences.This paper presents a summary of the results and recommendations from the conference, including: A review of current research on solid state electrolytes and their interfaces with an emphasis on both applied and basic studies. The research includes theoretical studies of solid polymer electrolytes (SPEs), lithium ion transport in SPEs, and simulations of the electrolyte–cathode interface. Experimental results are presented on ion transport phenomena in SPEs (NMR and X–ray) and mechanical stresses on electrodes, among other topics. The issues addressed center on improved stability of and transport at interfaces, improved conductivity in the SPE, and higher transference numbers. A synopsis of problem areas and barriers to future progress in this field, the solution to which would benefit from both new theoretical treatment and the application of recent advances in experimental techniques. A summary of the recommendations and suggestions of the workshop participants are presented, organized into programmatic and technical recommendations and suggestions.