The cylinder-to-cylinder rolling contact fatigue rig is a line contact type of accelerated test rig. As an example of the test results from this rig, an investigation of the influence of the full crowning value on the rolling contact fatigue life is described. In the contact stress distribution along the axis of the line contact, the contact stress at the crowning edge, P_edge, has a 1.4 times larger influence on the rolling contact fatigue life than the maximum contact stress, P_max, at the center of the contact area; the rolling fatigue life is therefore determined by P_max or 1.4 P_edge, whichever is larger. This result can also be interpreted by the contact stress at the edge, Q_max, calculated by Moyer's method. Then the rolling fatigue life is determined by P_max or Q_max, whichever is larger. The optimum crowning value is the value which gives P_max = 1.4 P_edge or P_max = Q_max.