The elastohydrodynamic grease lubrication problem is usually associated with highly stressed machine elements such as rolling bearings, gears, cams and traction drives. In this thesis, a numerical analysis of thermal elastohydrodynamic grease lubrication problems of line contacts is carried out using Herschel-Bulkley model. The Reynolds equation and the energy equation of Herschel-Bulkley model grease have been developed taking the effects of temperature and rheological characteristics on the performance of grease TEHL into account. The problem is systematically analyzed using the finite difference method(FDM), the Newton-Raphson method and the Gauss-Seidel method. The Newton-Raphson method is used to solve the coupled Reynolds and elasticity equation and the energy equation is solved by the Gauss-Seidel method with proper boundary conditions. The viscosity and the density are assumed to be constant across the film. To solve the energy equation, two methods are developed : one with assuming a parabolic lubricant temperature profile across the film and another with integrating the energy equation across the film. Different viscosity formulas such as Barus and Roelands are used in these methods. The pressure distribution, the shape of grease film, mean film temperature and surface temperature of solid wall in line contacts are obtained. The findings are summarized as follows : The thermal effects on the viscosity and the density of grease cannot be neglected at high speed condition. The thermal effects on the minimum film thickness become remarkable at high rolling speed condition. The difference between the minimum film thicknesses obtained by means of the Barus viscosity and the Roelands viscosity is about 10%. In order to obtain the more accurate numerical solution, it is very critical to use a proper viscosity formula, which accurately fits experimentally measured viscosity values. The Roelands viscosity is better than Barus viscosity for this purpose. The difference between the results of the method in which mean film temperatures are obtained by assuming a parabolic lubricant temperature profile across the film and of the method in which mean film temperatures are obtained by integrating the energy equation across the film is insignificant. The effect of yield stress of Herschel-Bulkley model on minimum film thickness is negligible, while the rheological index and viscosity parameter have significant effect on minimum film thickness. The larger rheological index and viscosity parameter, the larger minimum film thickness.