The Xth Symposium on Fast Ionic Conductors marks the anniversary of such biannual meetings of the Polish Solid State Ionics Society. The Symposium was held in September 13–17, 2006 at Augustów in Poland and brought together scientists working on different topics from the field of Solid State Ionics. The meeting brought together 73 participants including PhD and MSc students, people from battery industry and experts in the field of fast ionic conductors and their applications in energy storage and conversion devices, sensors and optical displays who presented a selection of lectures on topics related to the scope of the Symposium. The conference was opened with the lecture on “ Progress in polymer batteries” presented by Prof. Michel Armand and closed with the lecture presented by Prof. Patrick Moseley on “The challenge of the HEV duty cycle—can lead-acid compete with NiMH and Li-ion”. Alltogether 33 plenary, keynote and short lectures were presented on topics related with the preparation, characterization and application of fast ionic conductors. The young participants of the Symposium presented their results during the poster session. This special issue of Journal of Power Sources is a collection of the best papers presented during the Symposium and covers the area of basic research on fast ionic conductors together with studies devoted to the application of these materials in batteries, fuel cells sensors and optical devices.