After the compilation of some general observations on the formation an
d mobility of protonic charge carriers in solids and liquids, proton c
onductivity in CsHSO4 and water is discussed in some detail. Proton co
nductivity is interpreted as a phenomenon between the solid and the li
quid state characterized by the structural and dynamic disorder of a h
ydrogen bond 'network'. Structural and chemical criteria for the appea
rance of high proton conductivity are formulated.