The standard theories of spin relaxation have not sufficiently emphasised the connection of this phenomenon to other linear irreversible processes and the role of entropy production has also not been clearly discussed.

In order to contribute to this problem, we start here with the linear relation between the generalised fluxes J_i and generalised forces X_i and we show the verification of the bilinear relation in fluxes and forces for the dissipation function Ψ_d In this connection a general expression for the diffusion-like equation is also calculated.

Furthermore, the phenomenological relaxation equation is developed, which shows the proportionalityof therelaxation rate 1/T₁ to the phenomenological coefficient L^E. The quantum-statistical treatment of relaxation starts also from the entropy production principle and one obtains a quantum-statistical alternative of the phenomenological coefficient L^E, which yields finally the molecular expression for the relaxation rate 1/T₁ . This result has been used for the treatment of spin-lattice relaxation by dipole-dipole interaction and one has obtained the same relation for 1/T₁, relaxation rate, as by other methods, using different starting points.