The basic features of the split Stirling refrigerator, driven by a linear compressor, are described. Friction of the compressor piston and of the regenerator, and the viscous losses due to the gas flow through the regenerator matrix are taken into account. The temp. at the cold end is an input parameter. The general equations are derived which are subsequently treated in the harmonic approxn. Examples are given of application of the relations for describing optimum-performance conditions as well as the interrelationship between cooler and heat-engine operation.