High temperature proton exchange membranes based on polybenzimidazoles (PBI) for fuel cells are reviewed. PBI membranes doped with phosphoric acid are the most successful system for high temperature operation of proton exchange membrane fuel cells (PEMFC). The review covers polymer synthesis, membrane casting, physicochemical characterization, and fuel cell technologies. High molecular weight PBI with modified structures has been synthesized to optimize membrane properties. Techniques for casting membranes from organic and acid solutions have been developed. Ionic and covalent cross-linking, as well as inorganic-organic composites, have been explored. Membrane characterizations include spectroscopy, water uptake, acid doping, thermal and oxidative stability, conductivity, electro-osmotic water drag, methanol crossover, gas solubility and permeability, and oxygen reduction kinetics. Fuel cell technologies such as electrode and MEA fabrication have been developed, and high temperature PEMFC has been successfully demonstrated at temperatures up to 200°C under ambient pressure. No gas humidification is mandatory, enabling the elimination of the complicated humidification system compared to Nafion cells. Other operating features of the PBI cell include easy control of air flow rate, cell temperature, and cooling. The PBI cell operating at above 150°C can tolerate up to 1% CO and 10 ppm SO₂ in the fuel stream, allowing for simplification of the fuel processing system and possible integration with the fuel cell stack and fuel processing units. Long-term durability with a degradation rate of 5 μV h⁻¹ has been achieved under continuous operation with hydrogen and air at 150–160°C. With load or thermal cycling, a performance loss of 300 μV per cycle or 40 μV h⁻¹ per operating hour was observed. Further improvement should be done by optimizing the thermal and chemical stability of the polymer, acid-base interaction and acid management, activity and stability of catalyst, and more importantly the catalyst support, as well as the integral interface between electrode and membrane.High temperature proton exchange membranes based on polybenzimidazoles (PBI) for fuel cells are reviewed. PBI membranes doped with phosphoric acid are the most successful system for high temperature operation of proton exchange membrane fuel cells (PEMFC). The review covers polymer synthesis, membrane casting, physicochemical characterization, and fuel cell technologies. High molecular weight PBI with modified structures has been synthesized to optimize membrane properties. Techniques for casting membranes from organic and acid solutions have been developed. Ionic and covalent cross-linking, as well as inorganic-organic composites, have been explored. Membrane characterizations include spectroscopy, water uptake, acid doping, thermal and oxidative stability, conductivity, electro-osmotic water drag, methanol crossover, gas solubility and permeability, and oxygen reduction kinetics. Fuel cell technologies such as electrode and MEA fabrication have been developed, and high temperature PEMFC has been successfully demonstrated at temperatures up to 200°C under ambient pressure. No gas humidification is mandatory, enabling the elimination of the complicated humidification system compared to Nafion cells. Other operating features of the PBI cell include easy control of air flow rate, cell temperature, and cooling. The PBI cell operating at above 150°C can tolerate up to 1% CO and 10 ppm SO₂ in the fuel stream, allowing for simplification of the fuel processing system and possible integration with the fuel cell stack and fuel processing units. Long-term durability with a degradation rate of 5 μV h⁻¹ has been achieved under continuous operation with hydrogen and air at 150–160°C. With load or thermal cycling, a performance loss of 300 μV per cycle or 40 μV h⁻¹ per operating hour was observed. Further improvement should be done by optimizing the thermal and chemical stability of the polymer, acid-base interaction and acid management, activity and stability of catalyst, and more importantly the catalyst support, as well as the integral interface between electrode and membrane.