The cam fatigue life of the translating roller---follower and translating flat---faced follower system has been investigated for polynomial and cycloidal displacement functions. Ioannides and Harris (IH) life prediction model are used to estimate the cam fatigue life. Computer program codes are written to calculate and simulate the different types of loads that act on the cam, the contact stresses in the cam and the followers and the 'volume under risk'. Ioannides---Harris theory is applied to the 'volume under risk' and expected fatigue life is calculated. The effects of cam base circle radius, cam angular velocity, roller---follower radius of curvature, cam thickness, follower eccentricity (offset), total lift (rise or fall), and second dwell angle on the fatigue life are studied for the translating roller---follower and flat---faced follower. In the cam translating roller---follower systems, it is found that the main design parameter governing the cam fatigue life is the cam base circle radius. In this system, the fatigue life curve shows an improvement in the fatigue life up to a critical cam base circle radius value. Any further increase in the cam base circle radius appears as a decrease in the fatigue life. While in the cam translating flat---faced follower systems, the fatigue life curve shows an improvement in the fatigue life up to a cam base circle radius value where the fatigue life was infinite. Also it is found that the cam radius of curvature plays the major rule in controlling the cam fatigue life in the flat---face follower systems.