Abstract: A pump jack comprises a rocker arm one end of which is fixed to the upper end of a sucker rod. The other limb of the rocker arm has rigidly affixed thereto a downwardly-extending drive support member and a large driven pinion is eccentrically and rotatably mounted at the lower end of this drive support member. The driven pinion is engaged by a chain, which also passes around a driving pinion fixed to the base of the pump jack. This drive arrangement reduces the acceleration and shock loadings imposed upon the sucker rod at the beginning of its upstroke and reduces the size and cost of the gearbox necessary to connect a prime mover to the driving pinion.