The efficiency of production systems consisting of a number of interconnected stations can be predicted from the characteristics of the stations when there is no internal storage. Formulae are developed for the efficiency of the basic connections, without and with redundancy. It is shown how the efficiency of more complex systems can be predicted using the basic formulae. The different types of redundancy, parallel, standby and splitting, are compared and it is shown that usually splitting, if feasible, is best. It is indicated how the results can be used to obtain upper and lower bounds on the efficiency with internal storage.