In this paper, the simultaneous influence of profile shape variation and running-in of the involute gear teeth on the surface load capacity of cylindrical gear pair was examined. Experimental investigations were carried out on spur gears in laboratory conditions, using back-to-back gear test rig. Different involute profile shapes are achieved by varying the gear teeth pressure angle. Different running-in regimes were achieved by varying the torque of the gear pair in the initial period of operation. By modifying the profile and adequate running-in in short period of time, the following are reduced: the intensity of wear, the amount of surface damage, friction on the contact surfaces of gear teeth. Greater benefits of higher pressure angle and running-in were observed with driven gears. It is shown that the negative sliding on the dedendum of the driving gears teeth has a greater effect on the generation of surface fatigue compared to the driven gears teeth, due to the direction of the friction force. The obtained results indicate that by varying the shape of the involute profile and running-in parameters, the surface load capacity of spur gears can be significantly improved, i.e. a longer operational life and greater efficiency of the gear drive in exploitation can be achieved.