Solid oxide fuel cell (SOFC) technology has made significant progress in the past 40 years and is currently in the early commercialization stage. The progress of the technology can be seen through review of the papers and presentations at the biennial International Symposium on Solid Oxide Fuel Cells initiated in 1989. This paper highlights key advances in materials development, understanding of electrode reactions and chemical interactions, and design, performance, durability and operation of single cells, multi-cell stacks and power systems. Power generation systems built with various design solid oxide fuel cells are described and their operating experiences reviewed, as well as challenges in reducing cell and system costs are summarized.