The intent of this recommended practice is to give information on the proper selection@ operation and maintenance of subsurface pumps so the best economical life can be obtained. The basic walking-beam sucker rod combination for producing fluids from the ground had its beginning in very early history. In more recent times@ many advances in design and metallurgy have evolved. The method is so popular that today approximately 90 percent of all artificially lifted wells are produced by a sucker rod pump. The downhole sucker rod pump is only one portion of the pumping system (see Figure 1). The other major components are the sucker rod string@ the surface pumping unit and the prime mover. For proper pumping operation and long maintenance-free runs@ all components of the system must be designed and sized properly@ taking into account well depth@ the amount and viscosity of fluids (oil@ water or gas) to be produced@ and abrasiveness and corrosiveness of fluids. A failure of any one of the pumping components will result in a shut down of the system@ resulting in a costly repair@ down-time and possible loss of production.