Recent progress in the study of divertor and scrape-off layer plasma phenomena inJET is reviewed. Three pumped divertors (Mark I, Mark IIA/AP and Mark IIGB) have beeninstalled and exploited under reactor relevant conditions. With increased divertor closure,the particle exhaust rate has increased and neutral compression factors of >100 have beenobtained with the Mark IIGB divertor. Helium enrichment factors of >0.2 have been measuredunder a wide range of conditions and satisfy the minimum requirements for ITER. Excellentpower handling has been demonstrated in all divertor configurations. Fast infrared camerameasurements exhibited broad deposition profiles during type I ELMs and energy densities of∼0.12 MJ/m2, which extrapolate to unacceptable levels for ITER. During the recentDT experiments, the co-deposition of tritium on cold shadowed surfaces in the inner divertorwas identified as an important form of long term tritium retention. This has serious implicationsfor the divertor design and tritium inventory in a next step tokamak. Core plasma purity hasnot improved with enhanced divertor closure or decreased main chamber neutral pressure.Studies of the chemical sputtering yield showed a dependence on surface temperature andhydrogen isotope. This accounts for the observation of increased carbon impurity productionin Mark II (at 500 K) relative to Mark I (at 300 K). The variation of the disruptive (L mode)density limit appears to be more strongly dependent on the local impurity production ratethan on the divertor geometry. Significant progress has been made in the study of divertordetachment, and volume recombination has been spectroscopically identified. With increasingisotope mass, detachment and the disruptive density limit occur at lower main plasma density,as predicted by the EDGE2D/NIMBUS codes. Using differential gas fuelling in the Mark IIGBdivertor, it was possible to modify the in-out asymmetry of the divertor plasma parametersand energy deposition for the first time.