- Abstract The effect of spin-orbit (SO) scattering in disordered mesoscopic systems is studied. In one dimension it is shown that any spin-independent thermodynamic or transport quantity can be expressed in terms of the same quantity in the absence of SO scattering, but with an effective magnetic flux. This leads to universal SO reduction factors of the harmonics. In particular, the conductance and its fluctuations are interrelated, within and beyond weak- localization theory. Generalizations to higher dimensions are discussed.