Interfaces between various components (ionic conducting, electronic conducting, mixed conducting, and electrically insulating) in a SOFC stack – their behavior and characteristics at operating temperatures of about 500^o to 1000^oC - play the key role in determining stack performance, reliability and durability/life. Interfaces in SOFC stacks include different types of material (metals, ceramics, and glasses) and require different properties (electrochemical, electrical, chemical, and mechanical): electrode-electrolyte (ceramic-ceramic interface; fast electrochemical reactions and minimal poisoning by contaminants required), electrode-interconnect (ceramic-metal interface; good electrical contacts and minimal contact losses/changes required), and sealant-interconnect/electrolyte (glass-metal/ceramic interfaces; adequate and reliable sealing/mechanical properties required). This paper provides an overview of characteristics and behavior of interfaces in SOFC stacks from the viewpoint of the requirements to enable practical applications and discusses certain technological aspects of cathode-interconnect interfaces, cathode-electrolyte interfaces in reverse operation, sealing interfaces, and interfaces in thin-film SOFCs operating at reduced temperatures.