There are two main factors that affect the service life of gears: surface durability andrntooth bending strength. Pitting and scoring is a phenomenon in which small particles arernremoved from the surface of the tooth due to the high contact stresses that are presentrnbetween mating teeth. After the investigation of shot pinning to increase the toothrnbending strength in gears, surface durability, in the form of macro and micropitting, isrnnow considered the dominant restriction on gear life and performance. The mainrnobjective of this thesis is to develop a method for the investigation of surface fatigue inrninvolute spur gears using finite element analysis. In achieving this two-dimensional &rnthree- dimensional equivalent contacting cylinders to model involute spur gear in contactrnand three- dimensional model of involute spur gear is used. Modeling of involutes spurrngear to study contact stress under different working conditions using CATIA & ANSYSrnsoftware is done. In addition parametric study to investigate the effect of loadingrncondition and material types in contact stress in gears, estimation of surface fatigue inrnrolling-sliding contact condition in spur gear by finite element method using ANSYSrnWorkbench software, effect of initial surface roughness on surface fatigue is studied. Thernresults obtained are compared with analytical method. Results from FEA using ANSYSrnshow that, a 2D model, estimates accurately contact pressure and stresses bellow therncontacting surface, where as the 3D Model estimate contact pressure with reasonablernaccuracy and failed to estimate stresses bellow the contacting surface. Results fromrnANSYS Workbench, for a 3D model of involute spur gear, shows that contact stress andrnshear stress results, correlated with theoretical formulation, with tolerable accuracy but,rnfailed to estimate von-Mises stress with acceptable accuracy. Results from ANSYSrnWorkbench, for a 3D model of equivalent contacting cylinders, show that contact stress,rnvon-Mises stress and shear stress results, correlated with theoretical formulation, withrntolerable accuracy. Finally, in estimating surface fatigue, this paper verified that, as thernsurface roughness increases the minimum fatigue life and the load caring capacity for arnspecific design life decreases.