Abstract. Present experiences on long term fuel retention in various devices show that the control of long-term tritium retention in future burning plasma devices is among the most challenging tasks in fusion development. In devices with carbon plasma facing components the overwhelming majority of the fuel is retained in hydrogen-rich carbon deposits built on various locations on the plasma facing sides but also on remote areas like the cold louvers at the entrance to the cryopump in the inner divertor of JET or other regions shadowed from direct plasma contact. The overall carbon deposition and fuel retention is governed by the primary carbon release, which is largely due to chemical hydrocarbon erosion, the long range transport of carbon in the SOL and confined plasma, the migration of the carbon in the vicinity of the target surfaces and the deposition conditions of the carbon impurities including the fraction of carbon to other condensable impurities streaming along with the carbon to the targets. The contribution summarises the latest results in this area based on measurements mainly in JET and TEXTOR and discusses the implications and predictions for ITER.