In many oil recovery processes, the aim is to recover the residual oil from the reservoir by increasing the capillary number via either decreasing the interfacial tension and/or increasing the displacing fluid viscosity. Hence, it is of particular importance to identify the form of the relative permeability curves at high-capillary-number flow. Despite the tremendous amount of studies published on the form of two-phase relative permeability curves at low-and ultra-low IFT (i.e., at high-capillary-number flow), a detailed review of these works is missing from the literature. Thus, this extensive review has been conducted with the hope to bridge the gap in information. The topics covered in this survey include the description of the relative permeability, factors affecting the relative permeability, relative permeability at high-capillary-number flow, and the IFT effect on the relative permeability of oil-water, gas-water, gas-oil, and gas-condensate systems.