More than half of the world oil reserves are heavy oil and bitumen, with vast deposits in Canada and Venezuela. They are more difficult to produce and refine than conventional oils. Even though the current commercial processes are based on thermal treatment of the heavy feeds, it is recognized that catalytic processes with hydrogen addition produce higher yields of liquid fractions with better quality. Most of the catalysts reported for upgrading of heavy oils and bitumen are similar to those commonly used in hydrotreating/hydroprocessing, i.e., Co(Ni)Mo(W) supported on alumina. However, it has been shown that catalyst’s textural properties need to be tuned up according to the targeted reactions (HDM/HAD or HDS/HDN) to avoid poisoning. Due to the problems associated with the poisoning of supported catalysts the use of unsupported particles have been proposed as an alternative for treating heavy oils and bitumen. Catalysts containing Mo, W, Ni and Co, tested under high pressure of hydrogen produce better conversions, and lipophillic precursors seem to perform better than emulsion or dispersed powders. Catalytic aquathermolysis of heavy oils with water soluble and oil-soluble metallic compounds, as well as amphiphilic and ionic liquids, or dispersed particles of different metals, have been reported to produce important viscosity reductions. Also, downhole processing has been proposed to produce synthetic oils in the reservoir thus reducing energy demands and decreasing emissions. Different process configurations have been reported: in situ combustion coupled with a supported NiMo/Al₂O₃; injection of an amphiphillic metal compound in aquathermolysis conditions; and the injection of catalytic nanoparticles dispersed in a hydrocarbon carrier with dissolved hydrogen. All of them report important viscosity reductions and increase in API gravity. Finally, only a few reports on kinetics for upgrading of heavy oils and bitumen can be found. Models based on lumps according to the distillation cuts seem to produce consistent results for different oils, catalysts and reaction conditions.